Climate of India – NDA Geography Notes

India has one of the world’s most fascinating climates. A single country experiences everything: the freezing cold of Ladakh, the scorching heat of Rajasthan, the heavy rains of Cherrapunji, and the pleasant weather of Kashmir. All of this is governed by a complex set of factors: latitude, altitude, distance from the sea, and most importantly, the monsoon.

The monsoon is the backbone of India’s climate and economy. About 75% of India’s annual rainfall comes from the Southwest Monsoon between June and September. When the monsoon is good, crops are good, and the economy grows. When it fails, droughts cause great suffering.

NDA tests this chapter through questions on monsoon mechanisms, El Niño effects, winter rainfall, the ITCZ, local winds, regional climate types, and specific rainfall data. These questions test both concepts and facts.

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Factors Affecting India’s Climate

Several factors work together to shape India’s climate.

Latitude: The Tropic of Cancer (23.5°N) passes through the middle of India. The south is tropical, hot throughout the year. The north is subtropical, with cooler winters and hotter summers.

Altitude: Higher places are cooler. The Himalayas protect northern India from bitterly cold Central Asian winds in winter. Hill stations like Shimla and Darjeeling are much cooler than nearby plains.

Pressure and winds: In winter, a high-pressure belt forms over Central Asia. Cold, dry winds blow outward from this belt, but the Himalayas block them from entering most of India. In summer, intense heating of the Indian subcontinent creates a low-pressure area that draws in the moisture-laden Southwest Monsoon winds from the Indian Ocean.

Distance from the sea: Coastal areas have moderate temperatures, neither very hot nor very cold. Places far from the sea (like Rajasthan) have extreme temperatures.

Ocean currents: Warm waters of the Indian Ocean and the Bay of Bengal supply the moisture that the monsoon winds carry to India.

The Western Ghats: These mountains act as a barrier to the Southwest Monsoon. The windward (western) side gets very heavy rain. The leeward (eastern) side is much drier, the rain shadow region.

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The Monsoon

The word monsoon comes from the Arabic word “Mausim” meaning season. It refers to the seasonal reversal of winds. India has two monsoons.

Southwest Monsoon (June to September): Summer Monsoon is the main rainy season, bringing about 75% of India’s annual rainfall.

Northeast Monsoon (October to December): Retreating Monsoon affects mainly Tamil Nadu and the southeastern coast. Tamil Nadu gets most of its rain from the Northeast Monsoon, unlike the rest of India, which depends on the Southwest Monsoon. Most of Tamil Nadu lies in the rain shadow of the Western Ghats and receives little from the Southwest Monsoon, but when the monsoon retreats, the winds become northeasterly, pick up moisture from the Bay of Bengal, and bring rain to Tamil Nadu between October and December.

Why the Summer Monsoon Blows from the Southwest

The summer monsoon winds blow from the southwest because of the Coriolis force combined with the general direction of wind from the Indian Ocean. [NDA 2011-I]

In summer, the Indian landmass heats up strongly, creating a powerful low pressure area over northwest India. Air from the high-pressure zone over the southern Indian Ocean rushes toward this low-pressure area. The Coriolis force deflects these winds to the right (northeastward) in the Northern Hemisphere, so they arrive in India from the southwest direction. The primary driving factor is low pressure conditions in northwest India that draw in the moisture-laden winds. [NDA 2011-I]

Mechanism of the Southwest Monsoon

Step 1: Heating of landmass: From March onwards, the Indian subcontinent heats up rapidly. By June, an intense low-pressure area develops over the Thar Desert in Rajasthan and the northwestern plains.

Step 2: Shift of the ITCZ: The Inter-Tropical Convergence Zone (ITCZ) is a belt of low pressure near the equator where the trade winds from the two hemispheres meet. In summer, the ITCZ shifts northward over the Indian subcontinent, to roughly 20°–25°N. This shift is crucial for pulling the monsoon winds deep into India. The ITCZ invites inflow of winds from different directions. [NDA 2012-II]

Step 3: Monsoon winds arrive: Moisture-laden winds from the Indian Ocean and the Bay of Bengal rush northward to fill the low-pressure zone. These are the Southwest Monsoon winds.

Step 4: Two branches of the Southwest Monsoon: The Southwest Monsoon splits into two branches when it hits India:

Branch	Entry Point	Areas Covered
Arabian Sea branch	Kerala coast	Kerala, Karnataka, Goa, Maharashtra, Gujarat, MP, Rajasthan
Bay of Bengal branch	Myanmar / Bangladesh coast	Northeast India, Bihar, UP, Delhi

Onset of the Southwest Monsoon: The monsoon first arrives on the Kerala coast around June 1, the official onset of the monsoon in India.

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Rainfall Distribution in India

Rainfall in India is very uneven. Some places get too much, others get too little.

Highest rainfall areas: Mawsynram in Meghalaya holds the record for the highest average annual rainfall in the world, around 11,872 mm per year. It is located in the Khasi Hills of Meghalaya. Cherrapunji (Sohra) is very close and also among the world’s wettest places. Agumbe in Karnataka is called the “Cherrapunji of South India.” The western coast, the windward side of the Western Ghats, and northeast India all receive very heavy rainfall.

Lowest rainfall areas: Jaisalmer in Rajasthan is among the driest places in India. Ladakh and western Rajasthan receive less than 100 mm per year. Leh in Ladakh gets very little rain as it lies in the rain shadow of the Himalayas.

Rainfall isohyets. Lines joining places of equal rainfall are called isohyets. The 50 cm isohyetal line roughly separates well-watered eastern India from the drier western India.

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El Niño and the Indian Monsoon

El Niño is a periodic warming of the central and eastern Pacific Ocean near Peru. When El Niño occurs, surface temperatures rise in the southern Pacific Ocean, disrupting the Walker Circulation, the normal east-west atmospheric circulation over the Pacific. The Walker Circulation shifts eastward from its normal position, reducing the moisture supply to the Indian monsoon. The result is deficient rainfall in India: droughts or a weak monsoon season.

Effects of El Niño: Surface temperatures rise in the southern Pacific Ocean, and rainfall in India is deficient. The Walker Circulation shifts eastward from its normal position, reducing monsoon rainfall. [NDA 2012-II]

El Niño is associated with weak monsoon and drought conditions in India. La Niña, the opposite phenomenon, a cooling of the Pacific, tends to strengthen the Indian monsoon.

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Winter in India

Western Disturbances

In winter (December to February), India’s northwest receives rainfall from a completely different source: Western Disturbances. These are cyclonic weather systems that originate in the Mediterranean Sea and travel eastward across Iran, Afghanistan, Pakistan, and into northwestern India. They bring winter rain and snowfall to Jammu & Kashmir, Himachal Pradesh, Uttarakhand, and Punjab and Haryana (light winter rain).

This winter rainfall is very important for the Rabi crops (wheat, mustard, and barley), grown in northern India in winter.

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Climate Seasons in India

India has four distinct seasons:

Season	Months	Key Feature
Winter	December to February	Cold, dry in north; Western Disturbances bring rain to NW India
Hot Weather (Summer)	March to May	Very hot; Loo winds in north; dust storms
Advancing Monsoon	June to September	Heavy rainfall; SW Monsoon; 75% of annual rain
Retreating Monsoon	October to November	NE Monsoon; rain over Tamil Nadu

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Local Winds of India

Loo is a hot, dry, and very strong wind that blows across the Indo-Gangetic Plain (northern India and Pakistan) in May and June. It blows from the west or northwest. Temperatures during the Loo can exceed 45°C. Prolonged exposure causes heatstroke and death.

Kaal Baisakhi (Nor’wester) refers to violent local thunderstorms that occur in West Bengal and Bangladesh during the late afternoon and evening in April and May (pre-monsoon season). They bring intense lightning, strong winds, and heavy rainfall. They are beneficial for jute, tea, and pre-Kharif crops in the region.

Mango Showers are pre-monsoon showers in Kerala and Karnataka that help in the ripening of mangoes, occurring just before the onset of the Southwest Monsoon.

Cherry Blossom / Coffee Showers are pre-monsoon showers in Karnataka that help the flowering of coffee plants.

Blossom Showers are pre-monsoon rains in Kerala.

Local Wind	Region	Season	Significance
Loo	NW India + Indo-Gangetic Plain	May–June	Hot, dry; heatstroke risk
Kaal Baisakhi (Nor’wester)	West Bengal, Bangladesh	April–May	Violent pre-monsoon storms; good for jute and tea
Mango Showers	Kerala, Karnataka	Pre-monsoon	Ripens mangoes
Coffee / Cherry Blossom Showers	Karnataka	Pre-monsoon	Helps coffee flowering
Blossom Showers	Kerala	Pre-monsoon	Pre-monsoon rains

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Monsoon Rainfall and Crops

India’s agriculture follows the monsoon. Kharif crops are sown in summer and harvested in autumn: rice, maize, jowar, bajra, cotton, sugarcane, and groundnut. They depend heavily on the Southwest Monsoon. Rabi crops are sown in winter and harvested in spring: wheat, mustard, barley, and peas. They depend on winter rain from Western Disturbances and stored soil moisture.

Season	Crops	Water Source
Kharif (summer–autumn)	Rice, cotton, sugarcane, maize, bajra	Southwest Monsoon
Rabi (winter–spring)	Wheat, mustard, barley, peas	Western Disturbances + stored moisture

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