NCERT Solutions Class 7 Social Science Chapter 2 Understanding the Weather

F R E E S T U D Y M AT E R I A L F O R E V E R Y S T U D E N T

CLASS 7 · SOCIAL SCIENCE

NCERT Solutions

Chapter 2: Understanding the
Weather

NCERT Textbook — Exploring Society: India And Beyond (Part I)

BOOK PAGES SECTIONS QUESTIONS MEDIUM

27 – 44 23 37 English

Solutions, notes, sample papers & more at 36 pages

Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

CLASS 7 · SOCIAL SCIENCE · EXPLORING SOCIETY: INDIA AND BEYOND (PART I)

NCERT Solutions — Chapter 2: Understanding the
Weather
Chapter 2 of Exploring Society: India and Beyond (Theme: India and the World: Land and the People) explains
what weather is, the five elements that make it up, and the instruments — thermometer, rain gauge,
barometer, wind vane, anemometer and hygrometer — with which we measure them. It ends with how the
India Meteorological Department turns those readings into the forecasts and colour-coded warnings that
keep people safe.

TEXTBOOK BOOK PAGES

Exploring Society: India and Beyond (Part I) (Class 27 – 44
7)

SECTIONS QUESTIONS

23 37

MEDIUM

English

The Big Questions — Page 27
Theme: India and the World: Land and the People

THE BIG QUESTIONS

Q1 How can we measure and monitor the weather around us?

We measure the weather by measuring its five elements, each with its own instrument and its
own unit. Monitoring means taking those readings at fixed times, day after day, and keeping a
record.

ELEMENT OF WEATHER INSTRUMENT UNIT

Temperature Thermometer degrees Celsius (°C)

Precipitation Rain gauge millimetres (mm)

Atmospheric pressure Barometer millibars (mb)

Wind Wind vane (direction), anemometer (speed) km/h

Humidity Hygrometer % relative humidity

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

All these instruments are kept together at a weather station, where readings are taken at
regular intervals. An Automated Weather Station (AWS) does the same job by itself, using
sensors, and can work in places where no one can stay — such as the AWS the National Disaster
Management Authority set up in 2023 on a glacial lake in Sikkim, more than 4800 metres above
sea level.

Why it happens: Words such as ‘hot’, ‘chilly’ or ‘heavy rain’ mean different things to
different people. Numbers on an agreed scale mean the same thing to everyone, so
a reading taken in Chennai can be compared with one taken in Kashmir.

Did you know? People have monitored the weather long before instruments existed
— by watching birds fly low, ants carrying their eggs to higher ground, frogs
croaking loudly, or pine cones opening and closing. This knowledge has been passed
down through generations and is still used in many parts of India, especially to
guess when the monsoon will arrive.

Q2 How do weather predictions help us prepare for events like heavy rain, storms,
drought and heat waves?

A prediction buys us time to act before the event arrives. Meteorologists study long records of
temperature, pressure, wind, rain and humidity, and use scientific methods to say what the
weather will do in the next few hours, days or weeks.

Heavy rain and storms at sea — fishermen are warned not to take their boats out, and an
entire coastal area can be evacuated if a cyclone is expected.
Heavy rain inland — local governments move people out of low-lying areas, keep pumps
and boats ready and stock relief material in advance.
Drought — farmers can choose a hardier crop or a shorter-duration variety, and water in
tanks and reservoirs can be rationed early instead of running out suddenly.
Heat waves — schools change their timings, hospitals prepare for heat stroke, and drinking-
water points are set up for people who work outdoors.
Everyday planning — pilots and sailors use wind data, farmers decide when to sow or
harvest, and a family knows whether to carry an umbrella on a school trip.

Why it matters now: Climate change is making extreme weather — droughts,
floods, cyclones and heat waves — more frequent. A forecast cannot stop a cyclone,
but it can decide how many people are still standing in its path when it lands.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

LET'S EXPLORE — Page 28
Weather and its Elements

LET'S EXPLORE

Q1 What are some of the words in your local language that you use to describe the
weather? Hot, cold, warm, chilly, crisp, pleasant, and so on, are commonly used
terms in English.

Make a list for your own language, and next to each word write what element of the weather it
describes — temperature, rain, wind or humidity. That is what turns the list into geography
instead of vocabulary.
Sample answer:

LANGUAGE WORDS FOR THE WEATHER ELEMENT IT
DESCRIBES

Hindi गम, ठं डा, सुहावना, उमस भरा, िठठुर न, झमाझम, बूदँ ाबाँद ी, लू temperature, humidity,
rain, wind

Tamil ெவய ல் (veyil, blazing sun), குள ர் (kulir, cold), ஈரப் ப தம் temperature, humidity
(eerappatham, humidity)

Bengali গরম (garam), ঠা া (thanda), ভ াপসা (bhyapsa, muggy), ঝড় (jhor, temperature, humidity,
storm) wind

Marathi ऊन, गारवा, दमट, िरमिझम, वादळ temperature, humidity,
rain, wind

Try this: Many Indian languages have a separate word for a very particular kind of
weather — loo for the hot dusty summer wind of north India, umas for sticky pre-
monsoon air, rimjhim for a gentle steady drizzle. Collect three such words that
English needs a whole phrase to translate.

Why it happens: A language grows the words its speakers need. Places that get four
months of rain have many words for rain; places that get a long dry summer have
many words for heat.

THINK ABOUT IT — Page 29

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Class 7 Social Science Chapter 2 Understanding the Weather
a g l AglaSem · NCERT Solutions

The elements of weather
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THINK ABOUT IT

.co a g l
a s emus imagine that Krishnan from Chennai is speaking with Amir in Kashmir.
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Let
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Q1
Krishnan tells Amir that it has become chilly in Chennai after it rained the previous
night. Amir asks him how cold it is. How will Krishnan explain to Amir how cold it is?

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After all, what is cold for Krishnan may be quite pleasant for Amir!
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Krishnan cannot explain it in words at all — he has to give Amir a number on a scale both of

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them know. He should say, “It is 20°C here,” instead of “it is chilly”.

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g the feeling
Why it.chappens: ‘Chilly’ is not a measurement, it is a feeling,aand
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depends on what your body is used to. Chennai is warm and humid almost all year,
a so 20°C feels cold to Krishnan. Kashmir has real winters with snow, so 20°C is a mild,

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pleasant day for Amir. The same air gives the two boys two opposite descriptions.
m a
em
.co agl
a s
gl what Krishnan's weather is like, and he can compare it
The moment Krishnan says “20°C”, the disagreement disappears. Amir may still think that 20°C

a
is pleasant, but he now knows exactly
with his own. This is precisely why the whole chapter is about measuring the weather with
common standards — the same is true of rain (millimetres), pressure (millibars), wind (km/h)
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and humidity (per cent).
m l as
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a s em Tip: Notice that Krishnan could add one more useful number — the humidity. Air at

agl 20°C that is damp after a night of rain feels much colder on the skin than dry air at
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20°C.

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LET'S EXPLORE — Pagea29

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Why we measure the weather

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LET'S EXPLORE
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What do you think could be some other reasons to measure the weather more

a precisely? (Hint: Think how knowing the weather a few hours or a few days in
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advance would help you plan some activities.)

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Precise measurement is what makes forecasting possible, and a forecast is useful to almost
everybody:

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Farmers — when to sow, when to irrigate, when to harvest, and when not to leave a cut crop
lying in the field.
Fishermen — whether it is safe to take a boat out to sea tomorrow.
Pilots and sailors — wind direction and speed decide take-off, landing and a ship's course.
Disaster management — a cyclone or flood warning gives a district time to evacuate people
and stock relief.
Schools and offices — a heat wave or heavy-rain warning can change timings or close a
school for a day.
Building and road work — concrete cannot be poured, and roads cannot be tarred, in the
rain.
Industry and museums — food processing needs controlled humidity; museums keep their
air dry to protect exhibits.
You — planning a picnic, a match, a wedding, a village fair or a school trip.

Why precision matters: “It may rain” helps nobody. “35 mm of rain between 4 p.m.
and 8 p.m. tomorrow” tells a farmer to stop irrigating, tells the municipality to clear a
drain, and tells you to carry an umbrella. The sharper the measurement, the sharper
the decision it supports.

LET'S EXPLORE — Page 30
Observing Nature's clues

LET'S EXPLORE FIELD WORK

Q1 Talk to elders in your neighbourhood and ask them how they predict the weather.
What signs do they observe? Document any sayings in your regional language that
refer to weather prediction.

How to do this well: talk to two or three elders — ideally a farmer, a fisherman or a gardener.
Ask them (i) what sign they watch, (ii) what it predicts, (iii) how many days ahead, and (iv)
whether it still works. Write each saying in your own script first, then a translation. Finally, check
a few of their signs against the IMD forecast for a week and note where they agreed.
Sample answer: Our neighbour Shantabai, who farms two acres, says she never needed a
forecast to know the monsoon was near.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

SIGN OBSERVED WHAT IT IS SAID TO PREDICT

Ants carrying their eggs to higher ground Heavy rain within a day or two

Birds flying unusually low A coming storm

Frogs croaking loudly in the evening Rain that night

Pine cones closing up Damp, humid air — rain on the way

Squirrels gathering and storing nuts A hard season ahead

Peacocks calling and dancing The first monsoon showers

A ring (halo) around the moon Rain within two or three days

Sayings collected: “Chiti ande le chali, barsat aane wali” — when the ants carry their eggs, the
rains are coming. In Tamil Nadu: “Kaakka kuḷithaal mazhai” — when the crow bathes in dust, rain
follows.

Why these signs work: They are not magic. Animals and plants respond to the very
same elements meteorologists measure. Ants shift their eggs because the ground is
becoming damp; pine cones close because the air's humidity has risen; birds fly low
because falling atmospheric pressure before a storm makes the air near the ground
easier to fly in. Traditional knowledge reads the same signals — through living
instruments instead of metal ones.

In-text Questions — Page 30
How meteorologists work

Q1 How do they do it? Do they just look up at the sky and guess?

No — they do not guess. Meteorology is the systematic study of the weather and how it
changes, and it is the basis of all forecasting.
Meteorologists work in three steps:

1. Measure. Instruments at weather stations record temperature, rainfall, pressure, wind and
humidity at fixed times every day.
2. Collect over time. The readings are gathered from hundreds of stations over months and
years, so that patterns can be seen — this is what the chapter calls statistics, the technique
of gathering and analysing data to detect patterns, understand events and make

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

predictions.
3. Predict. Scientific methods are applied to that data to say how the weather in a region will
behave in a few hours, a few days, or even a few weeks.

Tip: Looking at the sky is still part of the job — a sudden dark bank of cloud is real
evidence. But an eye can only see the sky above one place at one moment.
Instruments see the whole country, day and night, and remember what they saw.

LET'S REMEMBER — Page 31
a) Temperature

LET'S REMEMBER

Recall In your Grade 6 Science textbook, Curiosity, you read about different types of
thermometers used for measuring the temperature — the clinical thermometer
and the laboratory thermometer. You also learnt about temperature scales. One
of them is the Celsius scale; another is the Fahrenheit scale. If, for instance, we
have a cool temperature of 15 degrees Celsius (noted as 15°C), it is the same as
59 degrees Fahrenheit (noted as 59°F).

Here is the Grade 6 idea in one place, ready to use in this chapter.

THERMOMETER WHAT IT MEASURES USUAL RANGE

Clinical thermometer Body temperature of a person about 35°C to 42°C

Laboratory thermometer Temperature of things in an experiment about −10°C to 110°C

Maximum–minimum thermometer Highest and lowest air temperature of a day used at weather stations

The two scales are two different rulers for the same thing:

0°C = 32°F (ice melts)

15°C = 59°F (a cool day — the book's example)

100°C = 212°F (water boils)
°F = (°C × 9 ÷ 5) + 32

Check the book's example: 15 × 9 ÷ 5 = 27, and 27 + 32 = 59. ✓

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Why two scales exist: The Celsius scale fixes 0 at the melting point of ice and 100 at
the boiling point of water, so it divides that gap into a neat 100 steps. The Fahrenheit
scale was made earlier with different fixed points and divides the same gap into 180
steps. India, and almost every weather service in the world, reports in °C.

Tip: A weather thermometer must never be kept in direct sunlight. It would then
record how hot the sunlit glass is, not how hot the air is.

DON'T MISS OUT — Page 32
The India Meteorological Department

DON'T MISS OUT

Q1 Can you think of a reason why rain arises from the sun?

Yes — the Sun is the engine that lifts water into the sky in the first place. Without the Sun's heat
there would be no water vapour, no clouds and therefore no rain.

Sun heats the sea, rivers, lakes, wet soil and leaves

→ water evaporates and rises as invisible water vapour

→ higher up the air is colder, so the vapour condenses into tiny droplets

→ millions of droplets together form a cloud

→ the droplets grow heavy and fall as rain

Page 8 of 36

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Class 7 Social Science Chapter 2 Understanding the Weather
a g l AglaSem · NCERT Solutions

co m
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m condensation
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evaporation
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sea, river, wet land
m l
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a gl The water cycle: the Sun's heat evaporates water, the vapour condenses high up into cloud, and the
cloud returns the water as rain.

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Why the motto is exact: The IMD's motto ādityāt jāyate vriṣhti — “From the sun
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arises rain” — comes from the Manusmṛiti, and the full line continues, “from rain

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comes food, and from food, living beings originate.” It is a chain: sunlight →
evaporation → rain → crops → life. Ancient observers had spotted the water cycle
. co
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without any instrument at all.
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agl Did you know? The India Meteorological Department was set up in 1875 and is one
of the oldest weather services in the world.
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ag32–33
LET'S EXPLORE — Pages

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Reading a temperature chart

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LET'S EXPLORE

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Here's a chart of the temperatures of a city in Madhya Pradesh. What is the
a maximum temperature recorded in the week shown here? What is the minimum?
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Calculate the range.
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These are the seven days g
a printed in the chart, 28.02.2025 to 06.03.2025:

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

DATE MAXIMUM (°C) MINIMUM (°C) RANGE FOR THE DAY (°C)

28.02.2025 29 16 13

01.03.2025 30 15 15

02.03.2025 31 17 14

03.03.2025 32 18 14

04.03.2025 30 17 13

05.03.2025 28 14 14

06.03.2025 29 15 14

Highest maximum in the week = 32°C on 03.03.2025

Lowest minimum in the week = 14°C on 05.03.2025

Range of temperature = 32 − 14

= 18°C

Why it happens: Range of temperature is simply maximum minus minimum. Over a
single day it tells you how sharply the air cools after sunset; over a week it tells you
how much the weather swung in that week. An 18°C swing is typical of an inland city
in late winter — clear skies let the ground heat strongly by day and lose that heat
quickly at night.

Try this: Work out the mean daily temperature for 03.03.2025 — (32 + 18) ÷ 2 = 25°C.
Do the same for all seven days and you will have the week's temperature profile.

Q2 Remember the conversation between Krishnan and Amir? If Krishnan said it was
20°C in Chennai and he was feeling a little cold, he and Amir would have a measure
they could understand. What do you think Amir's reaction to Krishnan's statement
might be?

Amir would probably laugh and say something like: “Twenty degrees? That is a pleasant spring
afternoon here! In Srinagar our winter mornings are near 0°C, and in January the water in the pipes
freezes. If it were 20°C in Kashmir we would be out playing without a jacket.”

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

The important thing is what has changed in the conversation. Earlier Amir could not picture
‘chilly’ at all. Now he knows the exact number and can compare it with his own experience — so
the two boys can finally disagree about the feeling while agreeing completely about the fact.

Why it happens: Our sense of hot and cold is relative to what our body is used to. A
Chennai body, used to 30–35°C almost all year, reads 20°C as cold. A Srinagar body,
used to winters near freezing, reads the same 20°C as mild. The thermometer settles
the fact; only the body decides the feeling.

Tip: This is exactly why the IMD publishes a ‘normal’ temperature (NOR) beside the
actual one. 6.5°C is a cold day in Srinagar only because Srinagar's normal for that
date is 8.9°C — the number by itself means nothing until you know the place.

In-text Questions — Page 33
b) Precipitation

Q1 If the news says that a particular place received 30 mm of rainfall in a day, what
does it mean?

It means that if none of the rain had run away, soaked in or evaporated, the rain that fell in that
day would have covered the whole area with a layer of water 30 millimetres (3 cm) deep.

Rainfall is measured as a depth, not as a volume

30 mm of rain on 1 square metre = 30 litres of water

30 mm of rain on 1 hectare = 3,00,000 litres

Why depth and not litres: Depth lets you compare any two places directly. A big city
and a small field both get “30 mm” if the rain over them was equally heavy — the
total number of litres would be wildly different, but the depth is the same. That is
what makes 30 mm in Chennai comparable with 30 mm in Cherrapunji.

Tip: As a rough guide, under 10 mm in a day is light rain, 30 mm is a good soaking
shower, and over 100 mm is the ‘extremely heavy rain’ the IMD marks on its warning
maps.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Q2 How is rainfall measured?

With an instrument called a rain gauge (Fig. 2.6). It has three parts, and each one has a job:

PART WHAT IT DOES

Collecting funnel Catches the rain that falls on a known, fixed area and guides it downwards

Measuring tube Stores the water that has been collected
(cylinder)

Measuring scale Marked in millimetres on the tube, so the depth of the collected water can be
read off

When it rains, the water falls into the funnel and is collected in the cylinder. The scale attached
to the cylinder gives the depth of the rainwater. If the height of the water collected is 5 mm,
the area received 5 mm of rainfall.

Tip: The reading is always taken at the same time every day — the IMD uses 0830
hours — so that every day's figure covers exactly 24 hours. If snow falls instead of
rain, it is allowed to melt first, and then measured.

Why the funnel matters: The funnel is wider than the tube, so a small depth of real
rainfall becomes a taller, easier-to-read column of water inside the narrow tube. The
scale is already adjusted for this, so you read the true rainfall directly.

LET'S EXPLORE — Page 34

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Making your own rain gauge

LET'S EXPLORE ACTIVITY

Q1 Make a rain gauge as shown in the diagram above. Place the rain gauge in an open
area, away from objects that might obstruct rain. Ensure that the rain gauge is on a
flat surface and will not tilt or topple with the wind. Using the measuring scale,
record the amount of rainwater collected at the same time every day, for a month.
(If there is snow, allow it to melt before taking the measurement.) Calculate the
average rainfall for every week in that month and comment on the variation from
week to week.

How to make it: Cut the top third off a straight-sided plastic bottle, invert that top and fit it into
the bottom part — it becomes the collecting funnel. Stick a strip of paper marked in millimetres
along the side of the lower part (or use a ruler), starting from the inside base. Put a few pebbles
at the bottom outside the measuring line, or set the bottle in a weighted tin, so wind cannot
topple it.
Rules that decide whether your readings are worth anything:

Open ground, away from trees, walls and the edge of a roof — anything overhead steals or
adds rain.
Flat, level surface; the mouth of the gauge must be horizontal.
Read at the same clock time every day, then empty the gauge.
Record ‘0’ on a dry day — a blank is not the same as a zero.
Let snow or hail melt before measuring.

Sample answer (a month during the monsoon):

WEEK DAILY READINGS (MM) TOTAL (MM) AVERAGE PER DAY (MM)

Week 1 0, 0, 12, 4, 0, 8, 4 28 28 ÷ 7 = 4.0

Week 2 15, 22, 30, 18, 6, 0, 7 98 98 ÷ 7 = 14.0

Week 3 2, 0, 0, 5, 11, 3, 0 21 21 ÷ 7 = 3.0

Week 4 0, 9, 26, 34, 12, 5, 0 86 86 ÷ 7 = 12.3

Total for the month = 28 + 98 + 21 + 86 = 233 mm

Average per week = 233 ÷ 4 = 58.25 mm

Page 13 of 36

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Class 7 Social Science Chapter 2 Understanding the Weather
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Comment on the variation: The rain did not arrive evenly. Weeks 2 and 4 gave over four-fifths
co m
of the month's total, while Weeks 1 and 3 were nearly dry. Rain in India comes in spells, not in a
e m.
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steady drizzle — a few days of active monsoon, then a break of a week, then another spell.

em a
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gl this matters: A farmer cannot plan on the monthly average of 233 mm. What
amatters
Why
is whether a dry break comes just when the young crop needs water. This is

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exactly why the IMD forecasts spells and breaks, not just seasonal totals.

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THINK ABOUT IT — Page 35
co m
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c) Atmospheric pressure

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THINK ABOUT IT

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a glQ1 Why do you think it would be important to measure atmospheric pressure? Who are
the people most likely to use such measurements?

m a s
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Because atmospheric pressure isgthe
a l earliest warning we have. Rain, wind and cloud tell you
what the weather is; a falling barometer tells you what it is about to become.

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Normal pressure at the sea coast ≈ 1013 mb
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Pressure

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Who uses these measurements:
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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

WHO WHY THEY NEED IT

Meteorologists To spot a depression forming and issue a storm or cyclone
warning

Fishermen and sailors To decide whether it is safe to go out to sea

Disaster management authorities To evacuate a coastal belt in time

Pilots and air traffic control Aircraft altimeters work on air pressure; wrong pressure means
wrong height

Mountaineers, trekkers, army units at high Low pressure means less oxygen — they must plan pauses to
altitude acclimatise

Farmers A falling barometer means rain is likely — do not leave a
harvested crop out

Why pressure predicts weather: Wind is simply air moving from high pressure to
low pressure. Where pressure drops sharply, air rushes in from all sides, is forced
upward, cools, condenses and forms thick cloud. So a low reading on a barometer is
really the first sign of that whole chain beginning.

Q2 People who journey to places at a high altitude are advised to make pauses on the
way to allow the body to acclimatise. Our army personnel serve in high-altitude
places like Khardung la in Ladakh, which is over 5600 metres above sea level. It is
hard to imagine how they live and work in places where the oxygen level is so low
— the atmospheric pressure there is generally about 650 millibars!

Compare the two numbers the chapter gives you:

At the sea coast: about 1013 mb

At Khardung La (over 5600 m): about 650 mb

Difference = 1013 − 650 = 363 mb — roughly a third of the air pressure is missing

Every breath a soldier takes at Khardung La therefore brings in only about two-thirds as much
oxygen as the same breath at the coast. The body responds by breathing faster and making the
heart work harder, which is why visitors feel breathless, dizzy or tired at high altitude.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

What acclimatising means: stopping for a day or two at an intermediate height, moving
slowly, drinking plenty of water and not exerting on the first days. Given that time, the body
makes more red blood cells and breathes more efficiently, so the same thin air carries enough
oxygen. Soldiers posted in Ladakh, Siachen and similar posts go through a staged
acclimatisation programme before they take up duty.

Why pressure falls with height: Atmospheric pressure is the weight of the air
above you. Climb a mountain and you leave part of the atmosphere below you, so
there is less air pressing down — the air becomes ‘thinner’, and the same lungful
holds fewer oxygen molecules.

Think about it further: The soldiers are not the only ones affected. Water boils at a
lower temperature up there, so cooking takes far longer; helicopters get less lift
from the thin air; and even a small wound heals more slowly. Respect for what our
army personnel manage at those heights is very much the point of this box.

THINK ABOUT IT — Page 36
d) Wind

THINK ABOUT IT

Q1 Have you seen seeds like these flying in the wind? What would happen to the seeds
if there was no wind?

Yes — the feathery parachute seeds of the dandelion, the cottony seeds of the semal (silk-
cotton) and madar (aak), and the winged seeds of the sal, maple and gulmohar that spin down
like tiny helicopters. All of them are built to ride on moving air.
If there were no wind:

Every seed would drop straight down and land in the shadow of its own parent plant.
Hundreds of seedlings would then be crowded into one small patch, fighting each other for
the same light, water and soil nutrients. Most would die.
The species could not spread to new ground — a plant cannot walk, so the wind is its
transport.
If a fire, flood or disease struck that one patch, the whole local population could be wiped
out, because there would be no offspring growing anywhere else.
Wind-pollinated plants — grasses, maize, bajra, pine — would also fail to set seed at all,
because their pollen too travels on the wind.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Why the shape of the seed matters: A parachute of fine hairs or a thin papery wing
gives the seed a large surface for very little weight. Moving air pushes such a seed
sideways for a long time before gravity brings it down — which is exactly how a seed
a few milligrams heavy can end up hundreds of metres from its parent.

Did you know? Wind is not the only carrier. Coconuts float to new shores on sea
water, burrs hook onto animal fur, and birds carry fruit seeds in their droppings. But
wind is the cheapest and most common way for a plant to send its children away
from home.

In-text Questions — Page 36
Measuring wind

Q1 So, how do we measure this direction and speed?

With two different instruments — one for where the wind comes from, one for how fast it blows.

INSTRUMENT HOW IT WORKS WHAT IT TELLS US

Wind vane (weather A rotating arm with a pointer at one end and a tail at the Wind direction
vane) other. The wind pushes the tail, so the pointer swings
round and points into the wind. It responds even to a
light breeze.

Wind sock A cloth tube on a mast, used on airport tarmacs and at Wind direction at a
factories that release ash or gases. It fills and points glance, for pilots
downwind. taking off and landing

Anemometer Three or four metal cups on a vertical shaft. The stronger Wind speed in km/h
the wind, the faster they spin; a meter at the bottom
counts the spins in a fixed time.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

tail pointer

Wind vane — direction Anemometer — speed
A wind vane turns until its pointer faces the wind; an anemometer's cups spin faster as the wind
grows stronger.

Why both readings are needed: Speed alone does not tell a pilot whether it is safe
to land, and direction alone does not tell a farmer how quickly the soil will dry.
Together they say where the weather is coming from and how forcefully — which is
why wind direction helps farmers predict where the rain will arrive from, and why a
higher wind speed dries the soil faster.

LET'S EXPLORE — Page 37
e) Humidity

LET'S EXPLORE

Q1 Where do you think humidity is likely to be more, Kochi or Jaipur? You might guess
that Kochi has higher humidity than Jaipur because it is located near the sea. But
how will we know for sure? If we had to compare the humidity level between Kochi
and Mangaluru, how would we do it? Discuss with your classmates.

Kochi is almost certainly the more humid of the two — and the guess is a good one, because
Kochi sits on the Arabian Sea coast of Kerala with sea water evaporating constantly beside it,
while Jaipur lies inland in Rajasthan, close to the dry Thar region, with no large water body
nearby.

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Class 7 Social Science Chapter 2 Understanding the Weather
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But a guess is not proof. To know for sure we must measure, exactly as we do with
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1. Use a hygrometer, the instrument that measures relative humidity, at each place.
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afternoon reading in the other.

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3. Take readings over several days and compare the averages, not one lucky day.
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And Kochi versus Mangaluru? Here
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small differences
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air. Beside a warm sea, sunshine evaporates sea water continuously and the sea
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LET'S REMEMBER — Page 38
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Evaporation and humidity

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When water evaporates, it causes a cooling effect. If the amount of water in the
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Evaporation cools. When water turns into vapour it takes heat away from the surface it

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Damp air slows evaporation. Air can only hold so much water vapour. If it is already nearly
full, very little more can evaporate into it — so wet clothes stay wet and sweat stays on your
skin on a rainy day.

Dry air (low humidity) → fast evaporation → strong cooling → you feel comfortable

Damp air (high humidity) → slow evaporation → little cooling → you feel sticky and hot

Why this explains ‘relative’ humidity: Air with no water vapour at all is rated 0%
(impossible in nature), and air completely saturated with vapour is 100%. So relative
humidity is really a measure of how full the air already is — and therefore of how
much more it can still take from your wet clothes, your skin, or a farmer's soil.

Check it yourself: Wet the back of your hand and blow on it. It feels cold, because
you are speeding up evaporation. Try it again on a very humid day — the cooling is
far weaker.

THINK ABOUT IT — Page 38
Relative humidity

THINK ABOUT IT

Q1 If the humidity in Delhi is at 52% while in Kochi it is 84%, in which of the two places
are wet clothes likely to dry faster? And where are you likely to sweat more,
assuming the temperature is the same in both places?

Wet clothes dry faster in Delhi, and you will sweat more in Kochi.

Delhi: 52% relative humidity → the air is only about half ‘full’ → plenty of room for more

vapour → fast evaporation → clothes dry quickly

Kochi: 84% relative humidity → the air is nearly saturated → little room left → slow
evaporation → clothes stay damp for hours

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Why you sweat more in Kochi: You do not actually produce much more sweat — it
simply does not evaporate. Sweat cools you only when it turns into vapour. In Kochi's
84% air it cannot evaporate fast enough, so it stays on your skin, your body stays hot
and keeps producing more. In Delhi's 52% air the same sweat evaporates quickly,
carries heat away, and your skin feels dry. That is exactly why 29°C in coastal Kochi
feels far more uncomfortable than 29°C in Delhi.

Tip: Notice that the question says “assuming the temperature is the same in both
places”. That is essential — if the temperatures differed, you could not separate the
effect of humidity from the effect of heat.

In-text Questions — Page 38
Measuring humidity

Q1 But how do we measure such numbers?

With an instrument called a hygrometer. It reads out the relative humidity as a percentage, on
this scale:

RELATIVE HUMIDITY WHAT IT MEANS

0% Air with absolutely no water vapour — impossible in natural conditions

20% – 40% Dry weather

60% – 80% Humid weather

100% Air saturated with water vapour — it can hold no more

There are several types of hygrometer, depending on the principle each one is based on. A
simple classical one uses two thermometers side by side, one with a wet cloth around its bulb;
the drier the air, the faster the water evaporates from the cloth, the more that thermometer
cools, and the bigger the gap between the two readings. Modern weather stations use
electronic sensors instead.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Why anyone bothers: Humidity measurement is of great importance in industry —
food processing, for instance, needs closely controlled humidity so that products
neither dry out nor spoil. Museums monitor humidity too, because they must keep a
dry environment to preserve their exhibits. And every daily weather bulletin quotes
it, because humidity decides how the temperature actually feels.

DON'T MISS OUT — Page 39
An automated weather station

DON'T MISS OUT

Q1 In 2023, the National Disaster Management Authority set up an AWS at a glacial
lake of Sikkim at an altitude of more than 4800 metres above sea level. The AWS
provides early information about upcoming weather conditions.

An Automated Weather Station is a self-operating system that uses sensors to measure and
record temperature, humidity, wind speed and direction, precipitation and atmospheric
pressure — and it does all this without any human being present.
Why a glacial lake, and why an AWS:

At over 4800 metres, on ice, no observer could sit and take readings four times a day
through the year. An AWS can.
Glacial lakes are dammed only by loose ice and rubble. Heavy rain or a sudden warm spell
can burst that dam and send a wall of water down the valley — a glacial lake outburst
flood.
Readings sent down from the AWS give early information — hours of warning for the towns
and hydel projects downstream in the Teesta valley.

Why AWS are spreading: They are used in agriculture, aviation, navigation and
environmental monitoring, and they deliver accurate, timely data at fixed intervals
without human intervention — which means weather can now be measured in
deserts, on mountains, on buoys at sea and on glaciers, exactly the places where the
most dangerous weather begins.

Did you know? Sikkim's own history shows why this matters — the state has seen a
devastating glacial-lake flood in the Teesta basin. Instruments placed at the source
are the cheapest form of protection a mountain state can buy.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

LET'S EXPLORE — Page 41
Predicting the Weather

LET'S EXPLORE

Q1 Discuss, in pairs, different situations in which weather predictions are helpful.
Make a list, and after you have completed it, share it and discuss it with the pair
sitting next to you. How many different categories of situations have you been able
to identify?

How to do this well: do not just make a long list — sort it into categories. That is what the last
line of the question is really asking. Work for five minutes in your pair, then join the next pair
and merge the two lists; the number of categories both pairs agree on is your answer.
Sample answer — six categories:

CATEGORY SITUATIONS WHERE A FORECAST HELPS

Farming Deciding when to sow, irrigate, spray or harvest; not leaving a cut crop in the field before
rain; protecting an orchard from hail

Travel and Flights delayed by fog or storms; ships and fishing boats staying in harbour; landslide and
transport snow closures on hill roads

Disaster Evacuating a coast before a cyclone; moving people out of flood plains; keeping relief
preparation material and boats ready

Health and daily Heat-wave advisories, changed school timings, drinking-water points, warm shelters during a
life cold wave

Work and industry Construction, road tarring, drying of grain, salt pans, brick kilns, solar and wind power
planning

Events and leisure Cricket matches, weddings, village fairs, school trips, treks and pilgrimages such as the
Amarnath or Kedarnath yatra

Why sorting matters: Two pairs will almost always produce the same twenty
examples. What differs is how many genuinely different kinds of use they see — and
that is the real measure of how well you have understood why a country runs a
weather service at all.

LET'S EXPLORE (Fig. 2.13, the IMD warning map) — Page 41

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India: weather warning for 19 May 2024
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LET'S EXPLORE MAP WORK

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conditions that the IMD is alerting people to?

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g‘Watch’, and large areas are under ‘Alert’ or ‘Warning’. It is
The first thing to notice is that on 19 May 2024 no subdivision of India is coloured green. Every
part of the country is under at leastaa
the height of the Indian summer, with the monsoon still to arrive — so the map shows two

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opposite kinds of trouble at the same time.

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COLOUR OF THE WHAT IT ROUGHLY WHERE IT IS ON THIS MAP

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Heavy rain / very heavy rain

Strong surface winds (wind sock) — over the Tamil Nadu–Kerala belt and interior Karnataka.
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coast, Gangetic West Bengal and the Andhra coast.

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dry, descending air while the south-west monsoon is already approaching Kerala,
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heat-wave half and a rain half — which is exactly what the next chapter, on climate,
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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Q2 Which states have warning signs?

‘Warning (Take Action)’ is the red level — the most serious on this map. On 19 May 2024 the red
subdivisions are:

RED (WARNING — TAKE ACTION) REASON SHOWN BY THE ICON

Rajasthan Severe heat wave, with thunder and lightning as well

Punjab Heat wave

Haryana, Chandigarh and Delhi Heat wave

Tamil Nadu Very heavy rain with strong surface winds

If ‘warning signs’ is read more loosely as “any colour other than green”, then the answer is every
state on the map — because none is green. The next level down, orange (Alert — Be
Prepared), covers Gujarat, Uttar Pradesh, Bihar, Assam and Meghalaya, Tripura, Kerala and part
of coastal Karnataka.

Tip: Read the map in two layers. The colour of a subdivision tells you how serious the
situation is; the icon printed on it tells you what the situation actually is. Both are
needed to answer any question about this map.

Q3 Which parts of India are likely to be free from severe weather?

Strictly speaking, none — there is no green ‘No Warning’ subdivision anywhere on this map.
The parts closest to normal weather are the yellow ‘Watch (Be Updated)’ areas, where people
are only asked to keep track of the forecast and no action is required. These include much of the
interior of the country — Madhya Pradesh, Chhattisgarh, Odisha, Telangana, interior Karnataka,
Maharashtra, Jharkhand — along with Jammu & Kashmir, Ladakh, Himachal Pradesh and
Uttarakhand in the north, where the only icon is thunder and lightning.

Why even these are only ‘watch’ and not ‘no warning’: Mid-May is the peak of the
pre-monsoon thunderstorm season. Afternoon heating over the heated land builds
tall storm clouds almost everywhere, so short spells of thunder and lightning are
expected over most of the country. A yellow subdivision is not a safe subdivision — it
is one where the weather is being kept an eye on.

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Tip: When you answer this in an examination, name the colour category first and
then the areas. That shows you have read the legend, not just guessed from the
map's shape.

Q4 Which states are likely to face heat wave conditions?

Look for the icon of a red thermometer with a small ‘+’. On the 19 May 2024 map it appears
over a broad belt running from the north-west across the northern plains to the east:

Red (Warning): Rajasthan, Punjab, Haryana–Chandigarh–Delhi.
Orange (Alert): Gujarat including Saurashtra and Kutch, Uttar Pradesh, Bihar.
Yellow (Watch): Madhya Pradesh, and pockets further east and south towards Vidarbha,
Jharkhand, Gangetic West Bengal and the Odisha coast; heat-wave markers also appear over
the Himachal Pradesh and Uttarakhand foothills and along the Konkan coast.

Why this belt and not the south: Heat waves need dry air, clear skies and no sea
breeze. In May, hot dry air blows in over north-west India, there is no cloud to cut
the sunshine, and the region lies far from any sea. The peninsula, by contrast, is
narrow — the sea is never far away, and the sea breeze keeps its maximum
temperatures lower.

Tip: Do not confuse the two thermometer icons. A thermometer with a ‘+’ means
heat wave; a thermometer inside a yellow circle means hot and humid, which is a
coastal condition, and a blue thermometer with a ‘–’ means a cold wave.

Q5 What are the causes for warning in Tripura and Lakshadweep?

PLACE COLOUR ON THE ICON SHOWN WHAT PEOPLE ARE BEING
MAP WARNED ABOUT

Tripura Orange — Alert (Be Dark cloud with a lightning Thunderstorms with lightning
Prepared) bolt

Lakshadweep Islands too small to Rain cloud, and a cloud Heavy rain along with thunder and
be shaded with a lightning bolt lightning

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Tripura lies in the North-East, where warm, extremely moist air from the Bay of Bengal is
pushed up against hills. That rising damp air builds tall thunderclouds, so pre-monsoon
thunderstorms with lightning — and the squally winds that come with them — are common in
May. Lightning is a serious hazard in this region for people working in open fields.
Lakshadweep is a group of small coral islands in the Arabian Sea, directly in the path of the
advancing south-west monsoon, which reaches this part of the sea before it reaches the Indian
mainland. Moist sea air and building cloud bring heavy rain and thunderstorms — dangerous
for the islanders' fishing boats and small inter-island craft.

Why the two warnings look alike but come from different causes: Tripura's
storms are built by moist air forced up over hills; Lakshadweep's come from moist air
rising over a warm sea as the monsoon current advances. The instrument readings
behind both would show the same thing — high humidity and falling pressure.

Before we move on ... — Pages 41–42
The chapter in four points

BEFORE WE MOVE ON

Point 1 Temperature, humidity, precipitation, wind and atmospheric pressure together
define the weather at a particular place.

These five are the elements of weather. No single one of them is the weather — the weather is
the combination of all five at one place at one moment.

ELEMENT WHAT IT IS

Temperature How hot or cold the atmosphere is

Precipitation Any form of water — rain, snow, sleet or hail — that falls from the sky

Atmospheric pressure The weight of the air above us, felt on the Earth's surface

Wind The movement of air, including its speed and direction

Humidity The amount of water vapour in the air

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Why all five are needed: 29°C tells you almost nothing on its own. Add 84%
humidity and you know it will feel sticky and oppressive; add a falling barometer and
you know a storm may be building; add a strong wind and you know the washing
will still dry. Weather is a description of the atmosphere, and it takes all five numbers
to make that description complete.

Point 2 The condition of these elements is measured using special instruments. Data
collected from these help us to monitor and predict the weather.

Each element has its instrument, and the instruments are brought together at a weather
station:

Thermometer → temperature (°C)

Rain gauge → precipitation (mm)

Barometer → atmospheric pressure (mb)

Wind vane and anemometer → wind direction and speed (km/h)

Hygrometer → humidity (% relative humidity)

Readings are taken at regular intervals, which is what makes mapping and forecasting
possible. An Automated Weather Station (AWS) does the same job with sensors alone, and is
used in agriculture, aviation, navigation and environmental monitoring, providing accurate and
timely information without human intervention.

Why the record matters more than any one reading: A single reading describes a
moment. Only a long series of readings, studied with scientific methods, reveals the
patterns from which meteorologists can predict what the weather will do next.

Page 28 of 36

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In different times or situations, one of the elements is dominant — for example,
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Point 3

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rainfall in July, the temperature in May and December, atmospheric pressure
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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

WEATHER CLIMATE

Period A moment, a day, a week Decades — usually 30 years or more

Changes Can change within hours Changes very slowly

Example “It is 32°C and raining in Kochi this “Kochi is hot and humid, with heavy rain from June
afternoon.” to September.”

How we Today's instrument readings Years of stored readings, averaged
know it

Why the chapters are in this order: Climate is built out of weather records. You
cannot describe the climate of a place until someone has measured its weather, day
after day, for many years — which is exactly what this chapter has been about.

Questions and activities — Pages 42–43
End-of-chapter exercises

QUESTIONS AND ACTIVITIES

Q1 Match the instrument with the weather element it measures. (1) Hygrometer (2)
Anemometer (3) Barometer (4) Thermometer (5) Rain gauge — (a) Precipitation (b)
Atmospheric pressure (c) Wind direction and speed (d) Humidity (e) Temperature

INSTRUMENT USED ELEMENT OF THE WEATHER UNIT

(1) Hygrometer (d) Humidity % relative humidity

(2) Anemometer (c) Wind direction and speed km/h

(3) Barometer (b) Atmospheric pressure millibar (mb)

(4) Thermometer (e) Temperature °C (or °F)

(5) Rain gauge (a) Precipitation millimetre (mm)

1–d 2–c 3–b 4–e 5–a

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Tip to remember them: The Greek roots give the answer away — hygros = wet
(hygrometer), anemos = wind (anemometer), baros = weight (barometer), therme =
heat (thermometer). A rain gauge needs no Greek at all.

A small caution: An anemometer alone measures wind speed; the direction is given
by the wind vane or wind sock that is normally mounted on the same mast. The
book pairs them together because at a weather station they always work as a pair.

Q2 Jyotsna is deciding what clothes to pack for her school trip to Mumbai in June. She
looks at the weather forecast, which predicts 29°C and 84% humidity. What would
be your advice to her?

Read the two numbers together. 29°C on its own is not very hot — but 84% relative humidity is
very high, so her sweat will hardly evaporate, and the day will feel far hotter and stickier than
29°C suggests. June in Mumbai is also the start of the monsoon, so heavy rain is likely.

29°C + 84% humidity → little evaporation → little cooling from sweat

→ it will feel hot, sticky and clammy, and washed clothes will take a very long time to dry

My advice to Jyotsna:

Pack light, loose, thin cotton clothes — light colours, and nothing tight. Cotton absorbs
sweat and lets air through; synthetics and denim will feel awful.
Carry more changes of clothing than she thinks she needs, because damp clothes will not
dry overnight in that humidity.
A raincoat or umbrella, and slippers or sandals that survive water — June is the monsoon
month in Mumbai.
A plastic bag or waterproof pouch for books, phone and tickets, and a spare pair of dry
footwear.
A water bottle — in humid heat you lose a lot of water through sweat even without feeling
very hot.
No woollens. Mumbai in June has no need of them.

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Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Why humidity, not temperature, is the deciding number here: Sweat cools the
body only when it evaporates. In air that is already 84% full of water vapour,
evaporation is very slow — so the body's cooling system barely works. That is why
coastal Mumbai at 29°C feels more oppressive than Delhi at 35°C in a dry May.

Q3 Imagine that a small group of students is setting up a rain gauge. Here are some
options for the site. 1. The school vegetable garden. 2. The terrace of the school
building. 3. Open ground with elevated platform. 4. Compound wall of school. 5.
Verandah of the school laboratory. Discuss in your group and finalise the site. Write
down the reasons for your decision.

Our group's decision: Site 3 — open ground with an elevated platform.
Reasons for choosing it:

It is open, so no tree, wall or roof overhead can block the rain or drip extra water in.
The elevated platform keeps the gauge above the ground, so mud does not splash into the
funnel and water flowing over the ground cannot enter it.
A platform gives a flat, firm, level base, so the gauge stays upright and will not tilt or topple
in the wind — exactly what the activity on page 34 insists on.
It is easy to reach at the same time every day, in the rain, without disturbing anyone.

Why we rejected the others:

SITE WHY IT IS NOT SUITABLE

1. School vegetable Plants overhead would intercept the rain; watering the garden would add water; the
garden soft, dug soil would let the gauge tilt

2. Terrace of the school Wind is much stronger and more turbulent up there, so it blows rain across the mouth
building of the gauge and the reading comes out too low; the gauge could also topple

4. Compound wall of A narrow, unstable perch; the wall shelters one side and splashes the other, and the
school gauge is likely to fall

5. Verandah of the It is roofed. Almost no rain will reach the gauge at all — the reading would be
school laboratory meaningless

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The rule behind all of this: A rain gauge must catch exactly the rain that would
have fallen on that piece of ground — no more and no less. Anything that shelters it,
splashes it, tilts it or exposes it to unusual wind will corrupt the reading. IMD
standards go further still: the mouth of the gauge is kept about 30 cm above
ground, on level open land, at least twice as far from any object as that object is tall.

Q4 Below is a chart taken from IMD, Jammu and Kashmir. Looking at the data
available, write a short script to report the weather conditions in different parts of
Jammu and Kashmir on the date shown. (Hint: Cover the temperature range,
maximum and minimum temperatures, humidity, precipitation, etc.) Note: ACT
means actual; NOR means normal; DEP is departure from normal; R/F is rainfall; S/N
is snowfall; TR means trace amount.

First, work out the range of temperature for each station (ACT max − ACT min):

STATION MAX MIN RANGE MAX 24-HR 24-HR HUMIDITY
(°C) (°C) (°C) DEP R/F S/N 0830 / 1730
(°C) (MM) (CM) (%)

Srinagar 6.5 0.2 6.3 −2.4 13.4 2.4 89 / 89

Qazigund 3.2 −0.4 3.6 −5.3 36.2 22.0 97 / 90

Pahalgam 1.1 −4.1 5.2 −4.5 19.4 23.0 96 / 96

Kupwara 5.1 −0.7 5.8 −3.4 21.9 10.0 97 / 94

Kukernag 2.6 −1.4 4.0 −4.0 35.2 30.0 96 / 97

Gulmarg −2.6 −7.6 5.0 −4.0 35.2 35.0 76 / 100

Muzafarabad 8.5 5.6 2.9 — 25.8 — 93 / —

Sample answer — a radio/TV script for the evening bulletin of 1 February 2024:
“Good evening. Here is the weather report for Jammu and Kashmir for today, the first of February
2024, prepared from the evening data of the India Meteorological Department.
It has been a cold, wet and snowy day across the Valley, with every station reporting a maximum
temperature below its normal for the date. Srinagar recorded a maximum of 6.5°C — 2.4 degrees
below normal — and a minimum of 0.2°C, giving a range of 6.3 degrees. Kupwara reached 5.1°C and
dipped to −0.7°C, while Qazigund managed only 3.2°C, a full 5.3 degrees below its normal, with a
night minimum of −0.4°C.

Page 33 of 36

ase
Class 7 Social Science Chapter 2 Understanding the Weather
a g l AglaSem · NCERT Solutions

The high hill stations were colder still. Pahalgam had a maximum of 1.1°C and a minimum of −4.1°C,
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and Kukernag 2.6°C and −1.4°C. Gulmarg was the coldest place in the region — the temperature
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.c in Muzafarabad it was the mildest, 8.5°C by day and 5.6°Caatg night — the smallest
there did not rise above freezing at all, with a maximum of −2.6°C and a bitter minimum of −7.6°C.

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Across the border

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day–night
There was widespread precipitation in the twenty-four hours ending at 8:30 this morning. Qazigund

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led with 36.2 mm of rain and 22 centimetres of snow; Kukernag received 35.2 mm and 30 centimetres

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of snow; and Gulmarg recorded the heaviest snowfall, 35 centimetres, with 35.2 mm of rain.
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Pahalgam had 19.4 mm and 23 centimetres of snow, Kupwara 21.9 mm and 10 centimetres, and
ag was the least affected, with 13.4 mm of rain and 2.4
Muzafarabad 25.8 mm of rain. Srinagar
centimetres of snow. Fresh precipitation continued through the day at most stations, though Srinagar

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reported only a trace amount between half past eight this morning and half past five this evening.
The air has been very damp everywhere. Morning relative humidity was betweene76
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and by evening

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agInl short: a cold, overcast and snowy day, colder than usual for the season, with heavy fresh snow in
Pahalgam

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the higher reaches. Travellers on the Jammu–Srinagar highway and near Gulmarg and Pahalgam
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should check road conditions before setting out, and residents are advised to guard against the cold.
Good night.”
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How to read the DEP column: DEP is the departure from normal — how far today
was from the average for that date. Every maximum-temperature DEP here is
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negative, which is the single clearest fact in the table: this was a colder-than-normal
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day right across the region. Interestingly the minimum-temperature DEPs are

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Tip: Muzafarabad's row has dashesco inmthe NOR and DEP columns — normals are not g l a
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available for that station, so s
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Weather is the state of the Earth's atmosphere at a particular time and place. Almost all

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weather happens in the troposphere, the lowest layer of air, 6 to 18 km thick.

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The five elements of weather are temperature, precipitation, atmospheric pressure, wind
and humidity.
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Words like ‘hot’ or ‘chilly’ mean different things to different people, so weather must be
measured on common standards — °C, mm, millibars, km/h and per cent.

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a g l Page 34 of 36

Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Each element has its own instrument: thermometer, rain gauge, barometer, wind vane and
anemometer, hygrometer. A weather station — often an Automated Weather Station
(AWS) — brings them all together.
From long records of these readings, meteorologists forecast the weather. The India
Meteorological Department (IMD), set up in 1875, issues maps that colour each
subdivision green, yellow, orange or red.
Accurate forecasts let fishermen stay ashore, let governments evacuate a coast before a
cyclone, and help farmers, pilots and sailors plan — which matters more than ever as
climate change makes extreme weather more frequent.

Page 35 of 36

Class 7 Social Science Chapter 2 Understanding the Weather AglaSem · NCERT Solutions

Quick revision

TERM WHAT IT MEANS INSTRUMENT / WHERE IT
UNIT APPEARS

Weather The state of the Earth's atmosphere at a — Page 28
particular time and place

Troposphere The layer of air closest to the ground (6–18 — Page 28
km) where almost all weather happens

Temperature How hot or cold the atmosphere is Thermometer; °C or °F Pages 31–32

Precipitation Water falling from the sky — rain, snow, Rain gauge; millimetres Page 33
sleet or hail (mm)

Atmospheric The weight of the air above and around us Barometer; millibar Pages 34–35
pressure (mb)

Wind Movement of air from high pressure to low Wind vane / Pages 36–37
pressure anemometer; km/h

Humidity The amount of water vapour in the air Hygrometer; % relative Pages 37–38
humidity

Range of Maximum temperature minus minimum °C Page 32
temperature temperature (usually over 24 hours)

Mean daily (Maximum + minimum temperature) ÷ 2 °C Page 32
temperature

Depression A dramatic fall in pressure (below 1000 mb) Barometer Page 35
that can grow into a storm or cyclone

Automated A self-operating set of sensors that records — Page 39
Weather Station weather data without human help

Meteorology The systematic study of weather and its — Page 30
evolution, the basis of forecasting

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