NCERT Textbook: Climate | Social Studies (SST) Class 9 PDF Download

 Page 1


I
n the last two chapters you have read about
the landforms and the drainage of
our country.  These are the two of the three
basic elements that one learns about the natural
environment of any area.  In this chapter you
will learn about the third, that is, the
atmospheric conditions that prevail over our
country.  Why do we wear woollens in December
or why it is hot and uncomfortable in the month
of May, and why it rains in June - July?  The
answers to all these questions can be found out
by studying about the climate of India.
Climate refers to the sum total of  weather
conditions and variations over a large  area for
a long period of time (more than thirty years).
Weather refers to the state of the atmosphere
over an area at any point of time. The elements
of weather and climate are the same, i.e.
temperature, atmospheric pressure, wind,
humidity and precipitation. You may have
observed that the weather conditions fluctuate
very often even within a day. But there is some
common pattern over a few weeks or months,
i.e. days are cool or hot, windy or calm, cloudy
or bright, and wet or dry. On the basis of the
generalised monthly atmospheric conditions,
the year is divided into seasons such as winter,
summer or rainy seasons.
The world is divided into a number of
climatic regions. Do you know what type of
climate India has and why it is so? We will
learn about it in this chapter.
•  The word monsoon is
derived from the Arabic word ‘mausim’ which
literally means season.
• ‘Monsoon’ refers to the seasonal reversal in the
wind direction during a year.
CLIMATE
The climate of India is described as the
‘monsoon’ type. In Asia, this type of climate
is found mainly in the south and the southeast.
Despite an overall unity in the general pattern,
there are perceptible regional variations in
climatic conditions within the country. Let us
take two important elements – temperature and
precipitation, and examine how they vary from
place to place and season to season.
In summer, the mercury occasionally
touches 50°C in some parts of the Rajasthan
desert, whereas it may be around 20°C in
Pahalgam in Jammu and Kashmir. On a winter
night, temperature at Drass in Jammu and
Kashmir may be as low as minus 45°C.
Thiruvananthapuram, on the other hand, may
have a temperature of 22°C.
In certain places there is a
wide difference between day and night
temperatures. In the Thar Desert the day
temperature may rise to 50°C, and drop down
to near 15°C the same night. On the other hand,
there is hardly any difference in day and night
temperatures in the Andaman and Nicobar
islands or in Kerala.
Let us now look at precipitation. There are
variations not only in the form and types of
precipitation but also in its amount and the
seasonal distribution. While precipitation is
mostly in the form of snowfall in the upper parts
of Himalayas, it rains over the rest of the
country. The annual precipitation varies from
over 400 cm in Meghalaya to less than 10 cm
in Ladakh and western Rajasthan. Most parts
of the country receive rainfall from June to
September. But some parts like the Tamil Nadu
4
2024-25
Page 2


I
n the last two chapters you have read about
the landforms and the drainage of
our country.  These are the two of the three
basic elements that one learns about the natural
environment of any area.  In this chapter you
will learn about the third, that is, the
atmospheric conditions that prevail over our
country.  Why do we wear woollens in December
or why it is hot and uncomfortable in the month
of May, and why it rains in June - July?  The
answers to all these questions can be found out
by studying about the climate of India.
Climate refers to the sum total of  weather
conditions and variations over a large  area for
a long period of time (more than thirty years).
Weather refers to the state of the atmosphere
over an area at any point of time. The elements
of weather and climate are the same, i.e.
temperature, atmospheric pressure, wind,
humidity and precipitation. You may have
observed that the weather conditions fluctuate
very often even within a day. But there is some
common pattern over a few weeks or months,
i.e. days are cool or hot, windy or calm, cloudy
or bright, and wet or dry. On the basis of the
generalised monthly atmospheric conditions,
the year is divided into seasons such as winter,
summer or rainy seasons.
The world is divided into a number of
climatic regions. Do you know what type of
climate India has and why it is so? We will
learn about it in this chapter.
•  The word monsoon is
derived from the Arabic word ‘mausim’ which
literally means season.
• ‘Monsoon’ refers to the seasonal reversal in the
wind direction during a year.
CLIMATE
The climate of India is described as the
‘monsoon’ type. In Asia, this type of climate
is found mainly in the south and the southeast.
Despite an overall unity in the general pattern,
there are perceptible regional variations in
climatic conditions within the country. Let us
take two important elements – temperature and
precipitation, and examine how they vary from
place to place and season to season.
In summer, the mercury occasionally
touches 50°C in some parts of the Rajasthan
desert, whereas it may be around 20°C in
Pahalgam in Jammu and Kashmir. On a winter
night, temperature at Drass in Jammu and
Kashmir may be as low as minus 45°C.
Thiruvananthapuram, on the other hand, may
have a temperature of 22°C.
In certain places there is a
wide difference between day and night
temperatures. In the Thar Desert the day
temperature may rise to 50°C, and drop down
to near 15°C the same night. On the other hand,
there is hardly any difference in day and night
temperatures in the Andaman and Nicobar
islands or in Kerala.
Let us now look at precipitation. There are
variations not only in the form and types of
precipitation but also in its amount and the
seasonal distribution. While precipitation is
mostly in the form of snowfall in the upper parts
of Himalayas, it rains over the rest of the
country. The annual precipitation varies from
over 400 cm in Meghalaya to less than 10 cm
in Ladakh and western Rajasthan. Most parts
of the country receive rainfall from June to
September. But some parts like the Tamil Nadu
4
2024-25
CLIMATE 27
•Why most of the world’s deserts are
located in the western margins of continents in the
subtropics?
Finally, relief too plays a major role in
determining the climate of a place. High mountains
act as barriers for cold or hot winds; they may
also cause precipitation if they are high enough
and lie in the path of rain-bearing winds. The
leeward side of mountains remains relatively dry.
FACTORS AFFECTING INDIA’S CLIMATE
Latitude
The Tropic of Cancer passes through the middle
of the country from the Rann of Kuchchh in the
west to Mizoram in the east. Almost half of the
country, lying south of the Tropic of Cancer,
belongs to the tropical area. All the remaining
area, north of the Tropic, lies in the sub-tropics.
Therefore, India’s climate has characteristics of
tropical as well as subtropical climates.
Altitude
India has mountains to the north, which have
an average height of about 6,000 metres. India
also has a vast coastal area where the
maximum elevation is about 30 metres. The
Himalayas prevent the cold winds from Central
Asia from entering the subcontinent. It is
because of these mountains that this
subcontinent experiences comparatively
milder winters as compared to central Asia.
Pressure and Winds
The climate and associated weather conditions
in India are governed by the following
atmospheric conditions:
• Pr Pr Pr Pr Pressur essur essur essur essure and sur e and sur e and sur e and sur e and surface winds; face winds; face winds; face winds; face winds;
• Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and
• W W W W Wester ester ester ester estern cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and
tropical cyclones tropical cyclones tropical cyclones tropical cyclones tropical cyclones.
India lies in the region of north easterly
winds. These winds originate from the
subtropical high-pressure belt of the northern
coast gets a large portion of its rain during
October and November.
 In general, coastal areas experience less
contrasts in temperature conditions. Seasonal
contrasts are more in the interior of the
country. There is decrease in rainfall generally
from east to west in the Northern Plains. These
variations have given rise to variety in lives of
people – in terms of the food they eat, the
clothes they wear and also the kind of houses
they live in.
• Why the houses in Rajasthan have thick
walls and flat roofs?
•  Why is it that the houses in the Tarai region and
in Goa and Mangalore have sloping roofs?
• Why houses in Assam are built on stilts?
CLIMATIC CONTROLS
There are six major controls of  the climate of
any place. They are: latitude, altitude,
pressure and wind system, distance from
the sea (continentality), ocean currents and
relief features.
Due to the curvature of the earth, the
amount of solar energy received varies
according to latitude. As a result, air
temperature generally decreases from the
equator towards the poles. As one goes from
the surface of the earth to higher altitudes,
the atmosphere becomes less dense and
temperature decreases. The hills are therefore
cooler during summers. The pressure and
wind system of any area depend on the
latitude and altitude of the place. Thus it
influences the temperature and rainfall
pattern. The sea exerts a moderating influence
on climate: As the distance from the sea
increases, its moderating influence decreases
and the people experience extreme weather
conditions. This condition is known as
continentality (i.e. very hot during summers
and very cold during winters). Ocean currents
along with onshore winds affect the climate of
the coastal areas, For example, any coastal
area with warm or cold currents flowing past
it, will be warmed or cooled if the winds are
onshore.
2024-25
Page 3


I
n the last two chapters you have read about
the landforms and the drainage of
our country.  These are the two of the three
basic elements that one learns about the natural
environment of any area.  In this chapter you
will learn about the third, that is, the
atmospheric conditions that prevail over our
country.  Why do we wear woollens in December
or why it is hot and uncomfortable in the month
of May, and why it rains in June - July?  The
answers to all these questions can be found out
by studying about the climate of India.
Climate refers to the sum total of  weather
conditions and variations over a large  area for
a long period of time (more than thirty years).
Weather refers to the state of the atmosphere
over an area at any point of time. The elements
of weather and climate are the same, i.e.
temperature, atmospheric pressure, wind,
humidity and precipitation. You may have
observed that the weather conditions fluctuate
very often even within a day. But there is some
common pattern over a few weeks or months,
i.e. days are cool or hot, windy or calm, cloudy
or bright, and wet or dry. On the basis of the
generalised monthly atmospheric conditions,
the year is divided into seasons such as winter,
summer or rainy seasons.
The world is divided into a number of
climatic regions. Do you know what type of
climate India has and why it is so? We will
learn about it in this chapter.
•  The word monsoon is
derived from the Arabic word ‘mausim’ which
literally means season.
• ‘Monsoon’ refers to the seasonal reversal in the
wind direction during a year.
CLIMATE
The climate of India is described as the
‘monsoon’ type. In Asia, this type of climate
is found mainly in the south and the southeast.
Despite an overall unity in the general pattern,
there are perceptible regional variations in
climatic conditions within the country. Let us
take two important elements – temperature and
precipitation, and examine how they vary from
place to place and season to season.
In summer, the mercury occasionally
touches 50°C in some parts of the Rajasthan
desert, whereas it may be around 20°C in
Pahalgam in Jammu and Kashmir. On a winter
night, temperature at Drass in Jammu and
Kashmir may be as low as minus 45°C.
Thiruvananthapuram, on the other hand, may
have a temperature of 22°C.
In certain places there is a
wide difference between day and night
temperatures. In the Thar Desert the day
temperature may rise to 50°C, and drop down
to near 15°C the same night. On the other hand,
there is hardly any difference in day and night
temperatures in the Andaman and Nicobar
islands or in Kerala.
Let us now look at precipitation. There are
variations not only in the form and types of
precipitation but also in its amount and the
seasonal distribution. While precipitation is
mostly in the form of snowfall in the upper parts
of Himalayas, it rains over the rest of the
country. The annual precipitation varies from
over 400 cm in Meghalaya to less than 10 cm
in Ladakh and western Rajasthan. Most parts
of the country receive rainfall from June to
September. But some parts like the Tamil Nadu
4
2024-25
CLIMATE 27
•Why most of the world’s deserts are
located in the western margins of continents in the
subtropics?
Finally, relief too plays a major role in
determining the climate of a place. High mountains
act as barriers for cold or hot winds; they may
also cause precipitation if they are high enough
and lie in the path of rain-bearing winds. The
leeward side of mountains remains relatively dry.
FACTORS AFFECTING INDIA’S CLIMATE
Latitude
The Tropic of Cancer passes through the middle
of the country from the Rann of Kuchchh in the
west to Mizoram in the east. Almost half of the
country, lying south of the Tropic of Cancer,
belongs to the tropical area. All the remaining
area, north of the Tropic, lies in the sub-tropics.
Therefore, India’s climate has characteristics of
tropical as well as subtropical climates.
Altitude
India has mountains to the north, which have
an average height of about 6,000 metres. India
also has a vast coastal area where the
maximum elevation is about 30 metres. The
Himalayas prevent the cold winds from Central
Asia from entering the subcontinent. It is
because of these mountains that this
subcontinent experiences comparatively
milder winters as compared to central Asia.
Pressure and Winds
The climate and associated weather conditions
in India are governed by the following
atmospheric conditions:
• Pr Pr Pr Pr Pressur essur essur essur essure and sur e and sur e and sur e and sur e and surface winds; face winds; face winds; face winds; face winds;
• Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and
• W W W W Wester ester ester ester estern cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and
tropical cyclones tropical cyclones tropical cyclones tropical cyclones tropical cyclones.
India lies in the region of north easterly
winds. These winds originate from the
subtropical high-pressure belt of the northern
coast gets a large portion of its rain during
October and November.
 In general, coastal areas experience less
contrasts in temperature conditions. Seasonal
contrasts are more in the interior of the
country. There is decrease in rainfall generally
from east to west in the Northern Plains. These
variations have given rise to variety in lives of
people – in terms of the food they eat, the
clothes they wear and also the kind of houses
they live in.
• Why the houses in Rajasthan have thick
walls and flat roofs?
•  Why is it that the houses in the Tarai region and
in Goa and Mangalore have sloping roofs?
• Why houses in Assam are built on stilts?
CLIMATIC CONTROLS
There are six major controls of  the climate of
any place. They are: latitude, altitude,
pressure and wind system, distance from
the sea (continentality), ocean currents and
relief features.
Due to the curvature of the earth, the
amount of solar energy received varies
according to latitude. As a result, air
temperature generally decreases from the
equator towards the poles. As one goes from
the surface of the earth to higher altitudes,
the atmosphere becomes less dense and
temperature decreases. The hills are therefore
cooler during summers. The pressure and
wind system of any area depend on the
latitude and altitude of the place. Thus it
influences the temperature and rainfall
pattern. The sea exerts a moderating influence
on climate: As the distance from the sea
increases, its moderating influence decreases
and the people experience extreme weather
conditions. This condition is known as
continentality (i.e. very hot during summers
and very cold during winters). Ocean currents
along with onshore winds affect the climate of
the coastal areas, For example, any coastal
area with warm or cold currents flowing past
it, will be warmed or cooled if the winds are
onshore.
2024-25
28 CONTEMPORARY INDIA-I
hemisphere. They blow southwards, get
deflected to the right due to the Coriolis force,
and move  towards the equatorial low-pressure
area. Generally, these winds carry little
moisture as they originate and blow over land.
Therefore, they bring little or no rain. Hence,
India should have been an arid land, but it is
not so. Let us see why?
Coriolis force: An apparent force caused by the
earth’s rotation. The Coriolis force is responsible for
deflecting winds towards the right in the northern
hemisphere and towards the left in the southern
hemisphere.  This is also known as ‘Ferrel’s Law’.
The pressure and wind conditions over
India are unique. During winter, there is a
high-pressure area north of the Himalayas.
Cold dry winds blow from this region to the
low-pressure areas over the oceans to the
south. In summer, a low-pressure area
develops over interior Asia, as well as, over
northwestern India. This causes a complete
reversal of the direction of winds during
summer. Air moves from the high-pressure
area over the southern Indian Ocean, in a
south-easterly direction, crosses the equator,
and turns right towards the low-pressure areas
over the Indian subcontinent. These are known
as the Southwest Monsoon winds. These winds
blow over the warm oceans, gather moisture
and bring widespread rainfall over the
mainland of India.
THE SEASONS
The monsoon type of climate is characterised
by a distinct seasonal pattern. The weather
conditions greatly  change from one season to
the other. These changes are particularly
noticeable in the interior parts of the country.
The coastal areas do not experience much
variation in temperature though there is
variation in rainfall pattern. How many seasons
are experienced in your place? Four main
seasons can be identified in India – the cold
weather season, the hot weather season, the
advancing monsoon and the retreating
monsoon with some regional variations.
The Cold Weather Season (Winter)
The cold weather season begins from mid-
November in northern India and stays till
February. December and January are the
coldest months in the northern part of India.
The temperature decreases from south to the
north. The average temperature of Chennai, on
the eastern coast, is between 24°– 25° Celsius,
while in the northern plains, it ranges between
10°C and 15° Celsius. Days are warm and
nights are cold. Frost is common in the north
and the higher slopes of the Himalayas
experience snowfall.
During this season, the northeast trade
winds prevail over the country. They blow from
land to sea and hence, for most part of the
country, it is a dry season. Some amount of
rainfall occurs on the Tamil Nadu coast from
these winds as, here they blow from sea to land.
In the northern part of the country, a feeble
high-pressure region develops, with light winds
moving outwards from this area. Influenced by
the relief, these winds blow through the Ganga
valley from the west and the northwest. The
weather is normally marked by clear sky, low
temperatures and low humidity and feeble,
variable winds.
A characteristic feature of the cold weather
season over the northern plains is the inflow of
cyclonic disturbances from the west and the
northwest. These low-pressure systems,
originate over the Mediterranean Sea and
western Asia and move into India, along with
the westerly flow. They cause the much-needed
winter rains over the plains and snowfall in the
mountains. Although the total amount of
winter rainfall locally known as ‘mahawat’ is
small, they are of immense importance for the
cultivation of ‘rabi’ crops.
The peninsular region does not have a well-
defined cold season. There is hardly any
noticeable seasonal change in temperature
pattern during winters due to the moderating
influence of the sea.
2024-25
Page 4


I
n the last two chapters you have read about
the landforms and the drainage of
our country.  These are the two of the three
basic elements that one learns about the natural
environment of any area.  In this chapter you
will learn about the third, that is, the
atmospheric conditions that prevail over our
country.  Why do we wear woollens in December
or why it is hot and uncomfortable in the month
of May, and why it rains in June - July?  The
answers to all these questions can be found out
by studying about the climate of India.
Climate refers to the sum total of  weather
conditions and variations over a large  area for
a long period of time (more than thirty years).
Weather refers to the state of the atmosphere
over an area at any point of time. The elements
of weather and climate are the same, i.e.
temperature, atmospheric pressure, wind,
humidity and precipitation. You may have
observed that the weather conditions fluctuate
very often even within a day. But there is some
common pattern over a few weeks or months,
i.e. days are cool or hot, windy or calm, cloudy
or bright, and wet or dry. On the basis of the
generalised monthly atmospheric conditions,
the year is divided into seasons such as winter,
summer or rainy seasons.
The world is divided into a number of
climatic regions. Do you know what type of
climate India has and why it is so? We will
learn about it in this chapter.
•  The word monsoon is
derived from the Arabic word ‘mausim’ which
literally means season.
• ‘Monsoon’ refers to the seasonal reversal in the
wind direction during a year.
CLIMATE
The climate of India is described as the
‘monsoon’ type. In Asia, this type of climate
is found mainly in the south and the southeast.
Despite an overall unity in the general pattern,
there are perceptible regional variations in
climatic conditions within the country. Let us
take two important elements – temperature and
precipitation, and examine how they vary from
place to place and season to season.
In summer, the mercury occasionally
touches 50°C in some parts of the Rajasthan
desert, whereas it may be around 20°C in
Pahalgam in Jammu and Kashmir. On a winter
night, temperature at Drass in Jammu and
Kashmir may be as low as minus 45°C.
Thiruvananthapuram, on the other hand, may
have a temperature of 22°C.
In certain places there is a
wide difference between day and night
temperatures. In the Thar Desert the day
temperature may rise to 50°C, and drop down
to near 15°C the same night. On the other hand,
there is hardly any difference in day and night
temperatures in the Andaman and Nicobar
islands or in Kerala.
Let us now look at precipitation. There are
variations not only in the form and types of
precipitation but also in its amount and the
seasonal distribution. While precipitation is
mostly in the form of snowfall in the upper parts
of Himalayas, it rains over the rest of the
country. The annual precipitation varies from
over 400 cm in Meghalaya to less than 10 cm
in Ladakh and western Rajasthan. Most parts
of the country receive rainfall from June to
September. But some parts like the Tamil Nadu
4
2024-25
CLIMATE 27
•Why most of the world’s deserts are
located in the western margins of continents in the
subtropics?
Finally, relief too plays a major role in
determining the climate of a place. High mountains
act as barriers for cold or hot winds; they may
also cause precipitation if they are high enough
and lie in the path of rain-bearing winds. The
leeward side of mountains remains relatively dry.
FACTORS AFFECTING INDIA’S CLIMATE
Latitude
The Tropic of Cancer passes through the middle
of the country from the Rann of Kuchchh in the
west to Mizoram in the east. Almost half of the
country, lying south of the Tropic of Cancer,
belongs to the tropical area. All the remaining
area, north of the Tropic, lies in the sub-tropics.
Therefore, India’s climate has characteristics of
tropical as well as subtropical climates.
Altitude
India has mountains to the north, which have
an average height of about 6,000 metres. India
also has a vast coastal area where the
maximum elevation is about 30 metres. The
Himalayas prevent the cold winds from Central
Asia from entering the subcontinent. It is
because of these mountains that this
subcontinent experiences comparatively
milder winters as compared to central Asia.
Pressure and Winds
The climate and associated weather conditions
in India are governed by the following
atmospheric conditions:
• Pr Pr Pr Pr Pressur essur essur essur essure and sur e and sur e and sur e and sur e and surface winds; face winds; face winds; face winds; face winds;
• Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and
• W W W W Wester ester ester ester estern cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and
tropical cyclones tropical cyclones tropical cyclones tropical cyclones tropical cyclones.
India lies in the region of north easterly
winds. These winds originate from the
subtropical high-pressure belt of the northern
coast gets a large portion of its rain during
October and November.
 In general, coastal areas experience less
contrasts in temperature conditions. Seasonal
contrasts are more in the interior of the
country. There is decrease in rainfall generally
from east to west in the Northern Plains. These
variations have given rise to variety in lives of
people – in terms of the food they eat, the
clothes they wear and also the kind of houses
they live in.
• Why the houses in Rajasthan have thick
walls and flat roofs?
•  Why is it that the houses in the Tarai region and
in Goa and Mangalore have sloping roofs?
• Why houses in Assam are built on stilts?
CLIMATIC CONTROLS
There are six major controls of  the climate of
any place. They are: latitude, altitude,
pressure and wind system, distance from
the sea (continentality), ocean currents and
relief features.
Due to the curvature of the earth, the
amount of solar energy received varies
according to latitude. As a result, air
temperature generally decreases from the
equator towards the poles. As one goes from
the surface of the earth to higher altitudes,
the atmosphere becomes less dense and
temperature decreases. The hills are therefore
cooler during summers. The pressure and
wind system of any area depend on the
latitude and altitude of the place. Thus it
influences the temperature and rainfall
pattern. The sea exerts a moderating influence
on climate: As the distance from the sea
increases, its moderating influence decreases
and the people experience extreme weather
conditions. This condition is known as
continentality (i.e. very hot during summers
and very cold during winters). Ocean currents
along with onshore winds affect the climate of
the coastal areas, For example, any coastal
area with warm or cold currents flowing past
it, will be warmed or cooled if the winds are
onshore.
2024-25
28 CONTEMPORARY INDIA-I
hemisphere. They blow southwards, get
deflected to the right due to the Coriolis force,
and move  towards the equatorial low-pressure
area. Generally, these winds carry little
moisture as they originate and blow over land.
Therefore, they bring little or no rain. Hence,
India should have been an arid land, but it is
not so. Let us see why?
Coriolis force: An apparent force caused by the
earth’s rotation. The Coriolis force is responsible for
deflecting winds towards the right in the northern
hemisphere and towards the left in the southern
hemisphere.  This is also known as ‘Ferrel’s Law’.
The pressure and wind conditions over
India are unique. During winter, there is a
high-pressure area north of the Himalayas.
Cold dry winds blow from this region to the
low-pressure areas over the oceans to the
south. In summer, a low-pressure area
develops over interior Asia, as well as, over
northwestern India. This causes a complete
reversal of the direction of winds during
summer. Air moves from the high-pressure
area over the southern Indian Ocean, in a
south-easterly direction, crosses the equator,
and turns right towards the low-pressure areas
over the Indian subcontinent. These are known
as the Southwest Monsoon winds. These winds
blow over the warm oceans, gather moisture
and bring widespread rainfall over the
mainland of India.
THE SEASONS
The monsoon type of climate is characterised
by a distinct seasonal pattern. The weather
conditions greatly  change from one season to
the other. These changes are particularly
noticeable in the interior parts of the country.
The coastal areas do not experience much
variation in temperature though there is
variation in rainfall pattern. How many seasons
are experienced in your place? Four main
seasons can be identified in India – the cold
weather season, the hot weather season, the
advancing monsoon and the retreating
monsoon with some regional variations.
The Cold Weather Season (Winter)
The cold weather season begins from mid-
November in northern India and stays till
February. December and January are the
coldest months in the northern part of India.
The temperature decreases from south to the
north. The average temperature of Chennai, on
the eastern coast, is between 24°– 25° Celsius,
while in the northern plains, it ranges between
10°C and 15° Celsius. Days are warm and
nights are cold. Frost is common in the north
and the higher slopes of the Himalayas
experience snowfall.
During this season, the northeast trade
winds prevail over the country. They blow from
land to sea and hence, for most part of the
country, it is a dry season. Some amount of
rainfall occurs on the Tamil Nadu coast from
these winds as, here they blow from sea to land.
In the northern part of the country, a feeble
high-pressure region develops, with light winds
moving outwards from this area. Influenced by
the relief, these winds blow through the Ganga
valley from the west and the northwest. The
weather is normally marked by clear sky, low
temperatures and low humidity and feeble,
variable winds.
A characteristic feature of the cold weather
season over the northern plains is the inflow of
cyclonic disturbances from the west and the
northwest. These low-pressure systems,
originate over the Mediterranean Sea and
western Asia and move into India, along with
the westerly flow. They cause the much-needed
winter rains over the plains and snowfall in the
mountains. Although the total amount of
winter rainfall locally known as ‘mahawat’ is
small, they are of immense importance for the
cultivation of ‘rabi’ crops.
The peninsular region does not have a well-
defined cold season. There is hardly any
noticeable seasonal change in temperature
pattern during winters due to the moderating
influence of the sea.
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CLIMATE 29
Figure 4.1 : Advancing Monsoon
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Page 5


I
n the last two chapters you have read about
the landforms and the drainage of
our country.  These are the two of the three
basic elements that one learns about the natural
environment of any area.  In this chapter you
will learn about the third, that is, the
atmospheric conditions that prevail over our
country.  Why do we wear woollens in December
or why it is hot and uncomfortable in the month
of May, and why it rains in June - July?  The
answers to all these questions can be found out
by studying about the climate of India.
Climate refers to the sum total of  weather
conditions and variations over a large  area for
a long period of time (more than thirty years).
Weather refers to the state of the atmosphere
over an area at any point of time. The elements
of weather and climate are the same, i.e.
temperature, atmospheric pressure, wind,
humidity and precipitation. You may have
observed that the weather conditions fluctuate
very often even within a day. But there is some
common pattern over a few weeks or months,
i.e. days are cool or hot, windy or calm, cloudy
or bright, and wet or dry. On the basis of the
generalised monthly atmospheric conditions,
the year is divided into seasons such as winter,
summer or rainy seasons.
The world is divided into a number of
climatic regions. Do you know what type of
climate India has and why it is so? We will
learn about it in this chapter.
•  The word monsoon is
derived from the Arabic word ‘mausim’ which
literally means season.
• ‘Monsoon’ refers to the seasonal reversal in the
wind direction during a year.
CLIMATE
The climate of India is described as the
‘monsoon’ type. In Asia, this type of climate
is found mainly in the south and the southeast.
Despite an overall unity in the general pattern,
there are perceptible regional variations in
climatic conditions within the country. Let us
take two important elements – temperature and
precipitation, and examine how they vary from
place to place and season to season.
In summer, the mercury occasionally
touches 50°C in some parts of the Rajasthan
desert, whereas it may be around 20°C in
Pahalgam in Jammu and Kashmir. On a winter
night, temperature at Drass in Jammu and
Kashmir may be as low as minus 45°C.
Thiruvananthapuram, on the other hand, may
have a temperature of 22°C.
In certain places there is a
wide difference between day and night
temperatures. In the Thar Desert the day
temperature may rise to 50°C, and drop down
to near 15°C the same night. On the other hand,
there is hardly any difference in day and night
temperatures in the Andaman and Nicobar
islands or in Kerala.
Let us now look at precipitation. There are
variations not only in the form and types of
precipitation but also in its amount and the
seasonal distribution. While precipitation is
mostly in the form of snowfall in the upper parts
of Himalayas, it rains over the rest of the
country. The annual precipitation varies from
over 400 cm in Meghalaya to less than 10 cm
in Ladakh and western Rajasthan. Most parts
of the country receive rainfall from June to
September. But some parts like the Tamil Nadu
4
2024-25
CLIMATE 27
•Why most of the world’s deserts are
located in the western margins of continents in the
subtropics?
Finally, relief too plays a major role in
determining the climate of a place. High mountains
act as barriers for cold or hot winds; they may
also cause precipitation if they are high enough
and lie in the path of rain-bearing winds. The
leeward side of mountains remains relatively dry.
FACTORS AFFECTING INDIA’S CLIMATE
Latitude
The Tropic of Cancer passes through the middle
of the country from the Rann of Kuchchh in the
west to Mizoram in the east. Almost half of the
country, lying south of the Tropic of Cancer,
belongs to the tropical area. All the remaining
area, north of the Tropic, lies in the sub-tropics.
Therefore, India’s climate has characteristics of
tropical as well as subtropical climates.
Altitude
India has mountains to the north, which have
an average height of about 6,000 metres. India
also has a vast coastal area where the
maximum elevation is about 30 metres. The
Himalayas prevent the cold winds from Central
Asia from entering the subcontinent. It is
because of these mountains that this
subcontinent experiences comparatively
milder winters as compared to central Asia.
Pressure and Winds
The climate and associated weather conditions
in India are governed by the following
atmospheric conditions:
• Pr Pr Pr Pr Pressur essur essur essur essure and sur e and sur e and sur e and sur e and surface winds; face winds; face winds; face winds; face winds;
• Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and Upper air circulation; and
• W W W W Wester ester ester ester estern cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and n cyclonic disturbances and
tropical cyclones tropical cyclones tropical cyclones tropical cyclones tropical cyclones.
India lies in the region of north easterly
winds. These winds originate from the
subtropical high-pressure belt of the northern
coast gets a large portion of its rain during
October and November.
 In general, coastal areas experience less
contrasts in temperature conditions. Seasonal
contrasts are more in the interior of the
country. There is decrease in rainfall generally
from east to west in the Northern Plains. These
variations have given rise to variety in lives of
people – in terms of the food they eat, the
clothes they wear and also the kind of houses
they live in.
• Why the houses in Rajasthan have thick
walls and flat roofs?
•  Why is it that the houses in the Tarai region and
in Goa and Mangalore have sloping roofs?
• Why houses in Assam are built on stilts?
CLIMATIC CONTROLS
There are six major controls of  the climate of
any place. They are: latitude, altitude,
pressure and wind system, distance from
the sea (continentality), ocean currents and
relief features.
Due to the curvature of the earth, the
amount of solar energy received varies
according to latitude. As a result, air
temperature generally decreases from the
equator towards the poles. As one goes from
the surface of the earth to higher altitudes,
the atmosphere becomes less dense and
temperature decreases. The hills are therefore
cooler during summers. The pressure and
wind system of any area depend on the
latitude and altitude of the place. Thus it
influences the temperature and rainfall
pattern. The sea exerts a moderating influence
on climate: As the distance from the sea
increases, its moderating influence decreases
and the people experience extreme weather
conditions. This condition is known as
continentality (i.e. very hot during summers
and very cold during winters). Ocean currents
along with onshore winds affect the climate of
the coastal areas, For example, any coastal
area with warm or cold currents flowing past
it, will be warmed or cooled if the winds are
onshore.
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28 CONTEMPORARY INDIA-I
hemisphere. They blow southwards, get
deflected to the right due to the Coriolis force,
and move  towards the equatorial low-pressure
area. Generally, these winds carry little
moisture as they originate and blow over land.
Therefore, they bring little or no rain. Hence,
India should have been an arid land, but it is
not so. Let us see why?
Coriolis force: An apparent force caused by the
earth’s rotation. The Coriolis force is responsible for
deflecting winds towards the right in the northern
hemisphere and towards the left in the southern
hemisphere.  This is also known as ‘Ferrel’s Law’.
The pressure and wind conditions over
India are unique. During winter, there is a
high-pressure area north of the Himalayas.
Cold dry winds blow from this region to the
low-pressure areas over the oceans to the
south. In summer, a low-pressure area
develops over interior Asia, as well as, over
northwestern India. This causes a complete
reversal of the direction of winds during
summer. Air moves from the high-pressure
area over the southern Indian Ocean, in a
south-easterly direction, crosses the equator,
and turns right towards the low-pressure areas
over the Indian subcontinent. These are known
as the Southwest Monsoon winds. These winds
blow over the warm oceans, gather moisture
and bring widespread rainfall over the
mainland of India.
THE SEASONS
The monsoon type of climate is characterised
by a distinct seasonal pattern. The weather
conditions greatly  change from one season to
the other. These changes are particularly
noticeable in the interior parts of the country.
The coastal areas do not experience much
variation in temperature though there is
variation in rainfall pattern. How many seasons
are experienced in your place? Four main
seasons can be identified in India – the cold
weather season, the hot weather season, the
advancing monsoon and the retreating
monsoon with some regional variations.
The Cold Weather Season (Winter)
The cold weather season begins from mid-
November in northern India and stays till
February. December and January are the
coldest months in the northern part of India.
The temperature decreases from south to the
north. The average temperature of Chennai, on
the eastern coast, is between 24°– 25° Celsius,
while in the northern plains, it ranges between
10°C and 15° Celsius. Days are warm and
nights are cold. Frost is common in the north
and the higher slopes of the Himalayas
experience snowfall.
During this season, the northeast trade
winds prevail over the country. They blow from
land to sea and hence, for most part of the
country, it is a dry season. Some amount of
rainfall occurs on the Tamil Nadu coast from
these winds as, here they blow from sea to land.
In the northern part of the country, a feeble
high-pressure region develops, with light winds
moving outwards from this area. Influenced by
the relief, these winds blow through the Ganga
valley from the west and the northwest. The
weather is normally marked by clear sky, low
temperatures and low humidity and feeble,
variable winds.
A characteristic feature of the cold weather
season over the northern plains is the inflow of
cyclonic disturbances from the west and the
northwest. These low-pressure systems,
originate over the Mediterranean Sea and
western Asia and move into India, along with
the westerly flow. They cause the much-needed
winter rains over the plains and snowfall in the
mountains. Although the total amount of
winter rainfall locally known as ‘mahawat’ is
small, they are of immense importance for the
cultivation of ‘rabi’ crops.
The peninsular region does not have a well-
defined cold season. There is hardly any
noticeable seasonal change in temperature
pattern during winters due to the moderating
influence of the sea.
2024-25
CLIMATE 29
Figure 4.1 : Advancing Monsoon
2024-25
30 CONTEMPORARY INDIA-I
The Hot Weather Season (Summer)
Due to the apparent northward movement of
the sun, the global heat belt shifts northwards.
As such, from March to May, it is hot weather
season in India. The influence of the shifting of
the heat belt can be seen clearly from
temperature recordings taken during March-
May at different latitudes. In March, the highest
temperature is about 38° Celsius, recorded on
the Deccan plateau. In April, temperatures in
Gujarat and Madhya Pradesh are around 42°
Celsius. In May, temperature of 45° Celsius is
common in the northwestern parts of the
country. In peninsular India, temperatures
remain lower due to the moderating influence
of the oceans.
The summer months experience rising
temperature and falling air pressure in the
northern part of the country. Towards the end
of May, an elongated low-pressure area
develops in the region extending from the Thar
Desert in the northwest to Patna and
Chotanagpur plateau in the east and
southeast. Circulation of air begins to set in
around this trough.
A striking feature of the hot weather season
is the ‘loo’. These are strong, gusty, hot, dry
winds blowing during the day over the north
and northwestern India. Sometimes they even
continue until late in the evening. Direct
exposure to these winds may even prove to be
fatal. Dust storms are very common during the
month of May in northern India. These storms
bring temporary relief as they lower the
temperature and may bring light rain and cool
breeze. This is also the season for localised
thunderstorms, associated with violent winds,
torrential downpours, often accompanied by
hail. In West Bengal, these storms are known
as the ‘Kaal Baisakhi’.
Towards the close of the summer season,
pre-monsoon showers are common especially,
in Kerala and Karnataka. They help in the early
ripening of mangoes, and are often referred to
as ‘mango showers’.
Advancing Monsoon (The Rainy Season)
By early June, the low-pressure condition over
the northern plains intensifies. It attracts, the
trade winds of the southern hemisphere. These
south-east trade winds originate over the
warm subtropical areas of the southern oceans.
They cross the equator and blow in a south-
westerly direction entering the Indian peninsula
as the south-west monsoon. As these winds
blow over warm oceans, they bring abundant
moisture to the subcontinent. These winds are
strong and blow at an average velocity of 30
km per hour. With the exception of the extreme
north-west, the monsoon winds cover the
country in about a month.
The inflow of the south-west monsoon into
India brings about a total change in the
weather. Early in the season, the windward
side of the Western Ghats receives very heavy
rainfall, more than 250 cm. The Deccan
Plateau and parts of Madhya Pradesh also
receive some amount of rain in spite of lying
in the rain shadow area. The maximum rainfall
of this season is received in the north-eastern
part of the country. Mawsynram in the
southern ranges of the Khasi Hills receives the
highest average rainfall in the world. Rainfall
in the Ganga valley decreases from the east to
the west. Rajasthan and parts of Gujarat get
scanty rainfall.
Another phenomenon associated with the
monsoon is its tendency to have ‘breaks’ in
rainfall. Thus, it has wet and dry spells. In
other words, the monsoon rains take place
only for a few days at a time. They are
interspersed with rainless intervals. These
breaks in monsoon are related to the
movement of the monsoon trough. For
various reasons, the trough and its axis keep
on moving northward or southward, which
determines the spatial distribution of rainfall.
When the axis of the monsoon trough lies over
the plains, rainfall is good in these parts. On
the other hand, whenever the axis shifts closer
to the Himalayas, there are longer dry spells
in the plains, and widespread rain occur in
the mountainous catchment areas of the
Himalayan rivers. These heavy rains bring in
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