India has a Tropical Monsoon type of climate.
It is called tropical because the Tropic of Cancer passes almost through the middle of the country.
It is called monsoon type because the seasonal reversal of winds and rainfall pattern is strongly controlled by the monsoon system.
India does not have one uniform climate everywhere.
Because of its large size, varied relief, long coastline, Himalayas, desert regions and island groups, different parts of India experience different climatic conditions.
Table of Contents
Why India Has A Diverse Climate
India’s climate varies from equatorial conditions to tundra-like conditions.
The southern part of India lies near the equator and experiences a tropical climate.
The northern part lies in the subtropical and temperate zone.
The Himalayan region experiences temperate and tundra-like conditions.
Western India has desert climate because the Thar Desert is located there.
The north-eastern states do not have a dry climate throughout the year.
The coastal regions have a coastal climate due to the influence of the sea.
The Andaman and Nicobar Islands experience an equatorial type of climate.
Despite these variations, the overall rhythm and character of Indian climate remains monsoonal.
Regional Variations In Temperature
Temperature varies sharply from place to place in India.
For example:
- Churu in Rajasthan may record 50°C or more on a June day.
- On the same day, Tawang in Arunachal Pradesh may record around 19°C.
- In winter, temperature may drop to -45°C in Drass, Ladakh.
- On the same winter day, Thiruvananthapuram or Chennai may record 20°C to 22°C.
These examples show how relief, latitude, altitude and distance from sea create strong temperature differences.
Regional Variations In Rainfall
Rainfall also varies greatly across India.
- Himalayan regions receive snowfall.
- Most other parts of India receive rainfall.
- Cherrapunji and Mawsynram in the Khasi Hills of Meghalaya receive more than 1080 cm rainfall in a year.
- Jaisalmer in Rajasthan rarely receives more than 9 cm rainfall in a year.
This shows that rainfall distribution in India is highly uneven.
Factors Determining The Climate Of India
The factors determining India’s climate are broadly divided into two groups:
- Factors related to location and relief.
- Factors related to air pressure and winds.
Factors Related To Location And Relief
Latitude
The Tropic of Cancer passes through the middle of India.
The area south of the Tropic of Cancer lies in the tropical zone.
The area north of it lies in the subtropical and temperate zone.
The tropical zone is closer to the equator.
So, it experiences high temperature throughout the year and has a smaller daily and annual range of temperature.
The northern part of India is farther from the equator.
So, it experiences more extreme climate with hot summers and cold winters.
Himalayan Mountains
The Himalayas act as an effective climatic divide.
They protect the Indian subcontinent from cold northern winds coming from Central and Eastern Asia.
Because of the Himalayas, India experiences milder winters compared to Central Asia.
The Himalayas also trap monsoon winds and force them to shed moisture within the Indian subcontinent.
This is why the Himalayas are important for both temperature and rainfall.
Distribution Of Land And Water
India is surrounded by water bodies on three sides in the south.
It has a high and continuous mountain wall in the north.
Land heats up and cools down faster than water.
Water heats up and cools down slowly.
This difference in heating and cooling creates seasonal pressure differences between land and sea.
These pressure differences cause reversal in the direction of monsoon winds.
Distance From The Sea
The sea has a moderating influence on climate.
Places near the sea do not experience extreme temperature.
Places far from the sea experience extreme heat in summer and extreme cold in winter.
This condition is called continentality.
For example, coastal cities like Mumbai and Chennai have moderate climates, while inland places like Delhi and Churu experience extreme temperatures.
Altitude
Temperature decreases with increase in height.
That is why hill stations are cooler than plains.
The chapter gives a useful comparison:
- Agra and Darjeeling are located near the same latitude.
- In January, Agra records around 16°C.
- Darjeeling records around 4°C because it is located at a higher altitude.
Relief
Relief affects temperature, air pressure, wind direction, wind speed and rainfall.
The windward side of the Western Ghats and Assam receive heavy rainfall during the southwest monsoon.
The southern plateau remains relatively dry because it lies on the leeward side of the Western Ghats.
This dry region is called a rain-shadow area.
Factors Related To Air Pressure And Winds
The climate and weather conditions of India are also controlled by atmospheric conditions.
These include:
- Surface pressure and winds.
- Upper air circulation.
- Jet streams.
- Western cyclonic disturbances.
- Tropical cyclones.
- Inter-Tropical Convergence Zone.
Mechanism Of Weather In Winter Season
During winter, the weather conditions of India are controlled by surface pressure, winds and upper air circulation.
Surface Pressure And Winds In Winter
During winter, high pressure develops over north-western India due to low temperature.
Winds blow from land to sea.
These winds are generally dry because they originate over land.
This is why most parts of India experience dry winter conditions.
However, the Tamil Nadu coast receives rainfall during the retreating or north-east monsoon season because the winds pick up moisture from the Bay of Bengal.
Jet Streams In Winter
During winter, the westerly jet stream plays an important role in India’s weather.
A jet stream is a narrow belt of high-altitude westerly winds in the troposphere.
Its speed varies from about 110 Km/hr in summer to about 184 Km/hr in winter.
One branch of the jet stream blows north of the Tibetan highlands.
The southern branch blows eastward, south of the Himalayas.
This southern branch strongly influences winter weather in India.
Western Cyclonic Disturbances
Western cyclonic disturbances are winter weather systems brought by the westerly flow from the Mediterranean region.
They mainly affect north and north-western India.
They are important because they bring winter rainfall to north-western India and snowfall to the Himalayas.
This rainfall is especially useful for rabi crops such as wheat.
Tropical Cyclones In Winter
Tropical cyclones originate over the Bay of Bengal and the Indian Ocean.
They are part of the easterly flow.
They affect coastal regions such as:
- Tamil Nadu
- Andhra Pradesh
- Odisha coast
These cyclones are often destructive because they bring high wind speed and torrential rain.
Mechanism Of Weather In Summer Season
During summer, the sun shifts northwards.
This causes a complete reversal in wind circulation over the Indian subcontinent at lower and upper levels.
Surface Pressure And Winds In Summer
By summer, intense heating of land creates a low-pressure area over north and north-western India.
The Inter-Tropical Convergence Zone, or ITCZ, shifts northwards.
By mid-July, it lies roughly parallel to the Himalayas between 20°N and 25°N.
This low-pressure belt attracts winds from different directions.
Moist maritime tropical air from the southern hemisphere crosses the equator and reaches India in a south-westerly direction.
This moist air current is known as the southwest monsoon.
Withdrawal Of Westerly Jet Stream
During summer, the westerly jet stream withdraws from the Indian region.
This withdrawal is related to the northward shift of the ITCZ.
Meteorologists consider the northward shift of the equatorial trough and the withdrawal of the westerly jet stream from north India to be closely related.
Easterly Jet Streams
An easterly jet stream flows over the southern part of the Indian peninsula in June.
Its maximum speed is about 90 Km/hr.
In August, it is confined to around 15°N latitude.
In September, it reaches up to around 22°N latitude.
These easterly jet streams do not extend north of 30°N latitude in the upper atmosphere.
Role Of Easterly Jet Streams
The easterly jet streams steer tropical depressions into India.
These depressions are very important for the distribution of monsoon rainfall.
The tracks of these depressions are among the areas with the highest rainfall in India.
Their frequency, direction and intensity decide the rainfall pattern during the southwest monsoon season.
Inter-Tropical Convergence Zone
The Inter-Tropical Convergence Zone, or ITCZ, is a broad trough of low pressure in equatorial latitudes.
It is the zone where the north-east and south-east trade winds converge.
Air tends to rise in this zone.
The ITCZ lies almost parallel to the equator but shifts north or south with the apparent movement of the sun.
ITCZ In July
In July, the ITCZ is located around 20°N to 25°N latitude over the Gangetic plain.
Here it is also called the monsoon trough.
This monsoon trough strengthens the thermal low over north and north-west India.
Because of the northward shift of ITCZ, trade winds from the Southern Hemisphere cross the equator between 40°E and 60°E longitude.
Due to the Coriolis force, they start blowing from south-west to north-east.
This gives rise to the southwest monsoon.
ITCZ In Winter
In winter, the ITCZ moves towards the Southern Hemisphere.
This causes reversal of winds from north-east to south and south-west.
These winds are called north-east monsoon winds.
Indian Monsoon
The monsoon is the most important feature of India’s climate.
Monsoon winds are seasonal winds that reverse their direction according to the season.
The Indian monsoon is mainly controlled by:
- Differential heating and cooling of land and water.
- Northward shift of the ITCZ in summer.
- Low pressure over north-west India.
- High pressure area east of Madagascar near 20°S over the Indian Ocean.
- Tibetan Plateau heating.
- Jet streams.
- Tropical depressions.
- Coriolis force.
Mechanism And Causes Of Indian Monsoon
Differential Heating
During summer, the Indian landmass heats up faster than the surrounding Indian Ocean.
This creates an intense low-pressure area over north and north-west India.
This is often called the heat low.
Shifting ITCZ
The sun’s northward movement shifts the ITCZ northwards.
It gets positioned over the Indo-Gangetic plain.
This elongated low-pressure zone is called the monsoon trough.
Wind Reversal
The south-east trade winds from the Southern Hemisphere cross the equator.
After crossing the equator, they are deflected by the Coriolis force.
They become southwest monsoon winds.
These winds blow from the Indian Ocean towards the heated landmass and carry huge moisture.
Role Of Jet Streams
The Subtropical Westerly Jet Stream shifts north of the Himalayas.
At the same time, the Tropical Easterly Jet Stream sets in over peninsular India.
This is important for the onset and strengthening of the monsoon.
Monsoon Burst
The arrival of the monsoon is often sudden.
It is marked by:
- Rapid increase in rainfall.
- Thunder and lightning.
- Fall in temperature.
- Sudden change in weather conditions.
This sudden onset is called the burst of monsoon.
Southwest Monsoon Season
The southwest monsoon season is also called the rainy season.
It generally lasts from June to September.
By early June, low-pressure conditions over north-western India become strong.
This attracts trade winds from the Southern Hemisphere.
These winds cross the equator, turn south-westerly and enter India as the southwest monsoon.
Onset Of Monsoon
The monsoon usually reaches:
- Kerala, Karnataka, Goa and Maharashtra coast in the first week of June.
- Interior parts of India later, sometimes by the first week of July.
The onset is marked by sudden rainfall, thunder and lightning.
Two Branches Of Southwest Monsoon
The southwest monsoon approaches India in two branches:
- Arabian Sea branch.
- Bay of Bengal branch.
Arabian Sea Branch
The Arabian Sea branch splits into three parts.
First Branch
The first branch strikes the Western Ghats.
These winds climb the slopes of the Western Ghats from about 900 to 1200 metres.
The windward side of the Sahyadris and the western coastal plain receive very heavy rainfall, between 250 cm and 400 cm.
After crossing the Western Ghats, the winds descend, become warmer and lose humidity.
This creates low rainfall on the eastern side of the Western Ghats.
This dry region is called the rain-shadow area.
Second Branch
The second branch strikes the coast north of Mumbai.
It moves along the Narmada and Tapi river valleys.
It causes rainfall in central India.
The Chotanagpur Plateau receives about 15 cm of rainfall from this branch.
Later, this branch enters the Ganga plains and merges with the Bay of Bengal branch.
Third Branch
The third branch strikes the Saurashtra Peninsula and Kachchh.
It then crosses west Rajasthan and moves along the Aravallis.
Because the Aravallis are roughly parallel to the direction of the winds, rainfall is low.
In Punjab and Haryana, it merges with the Bay of Bengal branch.
Together, these branches bring rainfall to the western Himalayas.
Bay Of Bengal Branch
The Bay of Bengal branch first hits the coast of Myanmar and parts of south-east Bangladesh.
The Arakan Hills along the coast of Myanmar deflect a large part of this branch towards the Indian subcontinent.
Because of this, the monsoon enters West Bengal and Bangladesh from the south and south-east, not directly from the south-west.
Two Branches Of Bay Of Bengal Monsoon
The Bay of Bengal branch splits into two parts:
- One branch moves westward along the Ganga plains and reaches Punjab.
- The second branch moves up the Brahmaputra Valley towards the north and north-east.
The north-eastern part of India receives very heavy rainfall.
Mawsynram in the southern ranges of the Khasi Hills receives the highest average rainfall in the world.
In the Ganga plains, rainfall decreases from east to west.
Breaks In Monsoon
Breaks in monsoon are rainless intervals or dry spells during the active monsoon season, especially in July and August.
Causes Of Breaks In Monsoon
The main cause is the temporary northward shift of the monsoon trough towards the foothills of the Himalayas.
When the trough lies over the plains, rainfall is widespread across the core monsoon zone from Gujarat to West Bengal.
When the trough shifts closer to the Himalayas, the plains experience dry spells.
At the same time, the Himalayan region, North-East India and parts of southern Peninsula receive intensified rainfall.
This may cause floods in the catchment areas of Himalayan rivers.
Other Causes
In the western coastal region, breaks are linked with winds blowing parallel to the coast without significant orographic uplift.
Global phenomena like El Niño can also cause prolonged and intense breaks in monsoon.
Withdrawal Of Monsoon
The withdrawal of monsoon is also called the retreating monsoon.
It takes place from October to December.
It is more gradual than the onset of the monsoon.
Mechanism Of Withdrawal
Southward Movement Of Sun And ITCZ
As the sun moves southward in September, the low-pressure monsoon trough weakens.
It starts shifting southward.
Formation Of High Pressure
The landmass begins to cool faster than the sea.
By October, a high-pressure area develops over northern India.
Wind Reversal
Surface winds reverse their direction.
They start blowing from north-east to south-west, from land to sea.
Gradual Retreat
The withdrawal begins from north-western India by early September.
It is complete from the entire subcontinent by mid-December.
October Heat
The retreating monsoon period is marked by clear skies, high temperature and high humidity.
This creates oppressive weather known as October Heat.
North-East Monsoon Rainfall
The north-easterly winds are generally dry because they blow from land to sea.
But after passing over the Bay of Bengal, they pick up moisture.
They bring rainfall to the Coromandel Coast, especially Tamil Nadu and Andhra Pradesh.
Indicator Of Withdrawal
A major indicator of monsoon withdrawal is:
- Cessation of rainfall for at least five consecutive days.
- Reduction in atmospheric moisture.
Seasons In India
Meteorologists recognise four main seasons in India:
- Cold Weather Season / Winter – November to February.
- Hot Weather Season / Summer – March to June.
- Southwest Monsoon Season / Rainy Season – June to September.
- Retreating Monsoon Season – September to October.
Cold Weather Season
The cold weather season begins from mid-November in northern India and lasts till February.
December and January are the coldest months in northern India.
Main Features
- Temperature decreases from south to north.
- Days are generally warm.
- Nights are cold.
- Frost is common in northern India.
- Higher slopes of the Himalayas receive snowfall.
- Western disturbances bring rainfall to north-western India.
Hot Weather Season
The hot weather season lasts from March to June.
During this season, the sun shifts northward and temperatures rise across most parts of India.
Main Features
- Strong heating of land.
- Low pressure develops over north-western India.
- Hot and dry winds blow in north India.
- Dust storms are common in some regions.
- Pre-monsoon thunderstorms occur in some areas.
Local Winds And Pre-Monsoon Rainfall
In northern India, hot and dry winds are known as loo.
In parts of eastern and north-eastern India, pre-monsoon thunderstorms bring rainfall.
These storms are locally important for crops and plantations.
Southwest Monsoon Season
The southwest monsoon season lasts from June to September.
It is the most important rainfall season of India.
Most parts of India receive the majority of their annual rainfall during this period.
Main Features
- Moist winds enter India from the Arabian Sea and Bay of Bengal.
- Rainfall begins with the burst of monsoon.
- Western coast and North-East India receive very heavy rainfall.
- Rain-shadow areas receive less rainfall.
- Rainfall decreases from east to west in the northern plains.
- Breaks in monsoon may occur in July and August.
Retreating Monsoon Season
The retreating monsoon season occurs mainly from September to October.
The southwest monsoon gradually withdraws from India.
Main Features
- Clear skies.
- High temperature and humidity.
- October Heat.
- Winds reverse direction.
- North-east monsoon brings rainfall to the Coromandel Coast.
- Tropical cyclones may affect eastern coastal areas.
Rainfall Distribution In India
Rainfall in India is unevenly distributed.
High Rainfall Areas
High rainfall is found in:
- Western coast.
- Western Ghats.
- North-eastern India.
- Parts of eastern Ganga plains.
- Himalayan foothills.
These regions are strongly influenced by the southwest monsoon and orographic rainfall.
Low Rainfall Areas
Low rainfall is found in:
- Western Rajasthan.
- Interior Deccan Plateau.
- Rain-shadow areas east of the Western Ghats.
- Parts of Ladakh and cold desert regions.
Rainfall Pattern
Important rainfall patterns include:
- Rainfall decreases from east to west in the northern plains.
- Western coast and North-East India receive maximum rainfall.
- Interior peninsular and north-western regions receive less rainfall.
- Snowfall is restricted mainly to the Himalayan region, especially Jammu and Kashmir, Himachal Pradesh, Uttarakhand and Sikkim.
Variability Of Rainfall
Rainfall in India varies from year to year.
This variation is measured using the Coefficient of Variation, or C.V.
Areas With Less Than 25 Per Cent Variability
These areas generally receive more than 100 cm annual rainfall.
They include:
- Western Coast.
- Western Ghats.
- Northeastern Peninsula.
- Eastern plains of the Ganga.
- Northeastern India.
- Uttarakhand.
- Himachal Pradesh.
- South-western part of Jammu and Kashmir.
Areas With 25 To 50 Per Cent Variability
This category occurs in the rest of India.
These areas receive annual rainfall between 50 cm and 100 cm.
Areas With More Than 50 Per Cent Variability
These areas receive less than 50 cm annual rainfall.
They include:
- Western Rajasthan.
- Northern part of Jammu and Kashmir.
- Interior parts of the Deccan Plateau.
Koeppen’s Classification Of Indian Climate
The chapter classifies India’s climate into major types according to Koeppen’s scheme.
Major Climate Types In India
| Climate Type | Code | Region / Feature |
|---|---|---|
| Tropical Monsoon | Am | Western coast and north-eastern states |
| Tropical Wet and Dry | Aw | Central and southern peninsular India |
| Semi-Arid Steppe | BSh | Rajasthan and Gujarat |
| Hot Desert | BWh | Parts of Rajasthan and Gujarat |
| Humid Subtropical With Dry Winter | Cwa / Cwb | Northern plains and Himalayan foothills |
| Highland Climate | H | High-altitude Himalayan regions |
Tropical Monsoon Climate
This climate is found along the western coast and in the north-eastern states.
It has a monsoon climate with a short dry winter season.
Tropical Wet And Dry Climate
This climate covers central and southern peninsular India.
It is similar to a tropical savanna climate with a dry winter season.
Semi-Arid Steppe Climate
This climate is found in parts of Rajasthan and Gujarat.
It is hot and semi-arid.
Hot Desert Climate
This climate is also found in parts of Rajasthan and Gujarat.
It is hot and arid.
Humid Subtropical Climate With Dry Winter
This climate is found in the northern plains and Himalayan foothills.
The dry winter is an important feature.
Highland Climate
This climate is found in the high-altitude Himalayan region.
It includes alpine and tundra-like climatic conditions.
Climate Of India At A Glance
| Topic | Key Fact |
|---|---|
| Main climate type | Tropical Monsoon |
| Reason for tropical climate | Tropic of Cancer passes through middle of India |
| Reason for monsoon climate | Seasonal reversal of winds |
| Highest temperature example | Churu may record 50°C or more |
| Cold desert example | Drass may fall to -45°C |
| Highest rainfall areas | Cherrapunji and Mawsynram |
| Low rainfall example | Jaisalmer rarely gets more than 9 cm |
| Main factors | Location, relief, air pressure and winds |
| Important relief factor | Himalayas |
| Important pressure factor | Differential heating of land and water |
| Important wind system | Monsoon winds |
| Important low-pressure belt | ITCZ |
| July ITCZ position | 20°N to 25°N over Gangetic plain |
| Monsoon trough | Northward-shifted ITCZ |
| Southwest monsoon season | June to September |
| Retreating monsoon | October to December |
| Breaks in monsoon | Dry spells in July and August |
| Rainfall variability measure | Coefficient of Variation |
| Main climate classification | Koeppen’s scheme |
FAQs On Climate Of India
What type of climate does India have?
India has a Tropical Monsoon type of climate.
Why is India’s climate called tropical monsoon climate?
It is called tropical because the Tropic of Cancer passes through the middle of India, and monsoon because the climate is controlled by seasonal reversal of winds.
Why does India have climatic diversity?
India has climatic diversity due to its large latitudinal extent, Himalayas, altitude differences, distance from sea, desert regions, coastline and monsoon winds.
Which place in India may record 50°C or more in summer?
Churu in Rajasthan may record 50°C or more during summer.
Which place in India may record -45°C in winter?
Drass in Ladakh may record temperatures around -45°C in winter.
Which places receive very high rainfall in India?
Cherrapunji and Mawsynram in Meghalaya receive very high rainfall.
Which place receives very low rainfall in India?
Jaisalmer in Rajasthan receives very low rainfall.
What are the main factors affecting India’s climate?
The main factors are location and relief, and air pressure and winds.
How do the Himalayas affect India’s climate?
The Himalayas block cold winds from Central Asia and force monsoon winds to shed moisture over India.
What is continentality?
Continentality means extreme climate found in places far from the sea, with very hot summers and very cold winters.
What is ITCZ?
The Inter-Tropical Convergence Zone is a low-pressure belt where trade winds converge and air rises.
What is the monsoon trough?
The monsoon trough is the northward-shifted ITCZ located over the Gangetic plain during summer.
What causes the southwest monsoon?
The southwest monsoon is caused by low pressure over north-west India, northward shift of ITCZ, cross-equatorial trade winds, Coriolis force and moisture from the Indian Ocean.
What is burst?
Monsoon burst is the sudden onset of monsoon rainfall with thunder, lightning and a rapid fall in temperature.
What are the two branches of the southwest monsoon?
The two branches are the Arabian Sea branch and the Bay of Bengal branch.
Why does the western coast receive heavy rainfall?
The western coast receives heavy rainfall because moisture-laden Arabian Sea winds rise along the Western Ghats and cause orographic rainfall.
What is a rain-shadow area?
A rain-shadow area is a dry area on the leeward side of a mountain where winds descend after losing moisture.
Why does rainfall decrease from east to west in the Ganga plains?
Rainfall decreases from east to west because the Bay of Bengal branch loses moisture as it moves westward.
What are breaks in monsoon?
Breaks in monsoon are dry spells or rainless intervals during the active monsoon season.
What causes breaks in monsoon?
Breaks occur mainly due to the northward shift of the monsoon trough towards the Himalayan foothills.
What is retreating monsoon?
Retreating monsoon is the withdrawal phase of the southwest monsoon, marked by reversal of winds and southward movement of the monsoon trough.
What is October Heat?
October Heat refers to hot and humid weather during the retreating monsoon season.
Which coast receives rainfall from the north-east monsoon?
The Coromandel Coast, especially Tamil Nadu and Andhra Pradesh, receives rainfall from the north-east monsoon.
What are the four seasons of India?
The four seasons are cold weather season, hot weather season, southwest monsoon season and retreating monsoon season.
What is rainfall variability?
Rainfall variability means year-to-year variation in rainfall and is measured using the Coefficient of Variation.
Which climate types are found in India according to Koeppen?
India has Tropical Monsoon, Tropical Wet and Dry, Semi-Arid Steppe, Hot Desert, Humid Subtropical with Dry Winter and Highland climates.
Last Moment Exam Cheat Sheet – Climate Of India
- India’s climate – Tropical Monsoon type.
- Tropical reason – Tropic of Cancer passes almost through the middle of India.
- Monsoon reason – Strong seasonal reversal of winds.
- South of Tropic of Cancer – Tropical climate.
- North of Tropic of Cancer – Subtropical and temperate climate.
- Himalayan region – Temperate and tundra type climate.
- Western India – Desert climate.
- Andaman and Nicobar – Equatorial climate.
- Churu – May record 50°C or more in June.
- Drass – May drop to -45°C in winter.
- Mawsynram and Cherrapunji – More than 1080 cm annual rainfall.
- Jaisalmer – Rarely more than 9 cm rainfall.
- Climate factors – Location and relief; air pressure and winds.
- Latitude – Controls tropical, subtropical and temperate conditions.
- Himalayas – Block cold winds and trap monsoon winds.
- Distance from sea – Controls continentality.
- Altitude – Temperature decreases with height.
- Relief – Controls windward and leeward rainfall.
- Jet stream – High-altitude westerly wind belt.
- Jet speed – About 110 Km/hr in summer and 184 Km/hr in winter.
- Western disturbances – Winter systems from Mediterranean region.
- Tropical cyclones – Affect Tamil Nadu, Andhra Pradesh and Odisha coasts.
- ITCZ – Low-pressure convergence zone near equator.
- ITCZ in July – Around 20°N to 25°N over Gangetic plain.
- Monsoon trough – ITCZ over Ganga plain.
- Southwest monsoon – Caused by cross-equatorial trade winds deflected by Coriolis force.
- High pressure near Madagascar – Affects Indian monsoon.
- Easterly jet stream – Steers tropical depressions into India.
- Southwest monsoon season – June to September.
- Monsoon burst – Sudden onset with heavy rain, thunder and lightning.
- Arabian Sea branch – Splits into three parts.
- Western Ghats windward side – Receives 250 cm to 400 cm rainfall.
- Rain-shadow area – East of Western Ghats.
- Bay of Bengal branch – Enters West Bengal and Bangladesh from south and south-east.
- Rainfall in Ganga plains – Decreases from east to west.
- Breaks in monsoon – Rainless intervals in July and August.
- Main cause of breaks – Northward shift of monsoon trough.
- Withdrawal of monsoon – October to December.
- October Heat – Hot and humid weather during retreating monsoon.
- North-east monsoon – Brings rain to Coromandel Coast.
- Four seasons – Winter, summer, southwest monsoon and retreating monsoon.
- Rainfall variability – Measured by Coefficient of Variation.
- Low variability areas – More than 100 cm rainfall.
- High variability areas – Less than 50 cm rainfall.
- Koeppen types – Am, Aw, BSh, BWh, Cwa/Cwb and H.