Indian Climate Notes for UPSC: Four Seasons, Western Disturbances, Jet Streams, El Nino, Cyclones, Local Winds, Rainfall Distribution and Climatic Regions Explained

India has a tropical monsoon climate, but within this big pattern there are many local differences: the snowy Himalaya, the hot desert of Rajasthan, the wet coasts of Kerala and the dry rain-shadow of the Deccan. For the UPSC Prelims, climate questions are asked on seasons, local winds, western disturbances, jet streams, El Nino, cyclones and climatic regions, and for the Mains, they link with agriculture, disasters and climate change. These notes explain the Indian climate as a whole, with tables, simple cause-and-effect explanations and quick revision points. To go deeper into the rainy season, you can also read our separate notes on the Indian Monsoon.

Why Climate Is a High-Yield Topic

Climate links geography with agriculture, economy, disasters and environment, so a single concept can give many questions. UPSC often asks about the cause behind a phenomenon, such as why the Coromandel Coast gets rain in winter, or why the Western Disturbances matter to wheat. A student who understands the mechanism can answer both the Prelims and the Mains. The topic is also very common in the news, in the form of heat waves, floods, cyclones and El Nino forecasts.

Factors Affecting the Indian Climate

The Four Seasons of India

Local Winds and Storms

• Loo: Hot and dry wind in the north-western plains in May and June.
• Kalbaisakhi (Nor'westers): Evening thunderstorms in West Bengal, Assam and Odisha in April and May, which help the tea, jute and rice.
• Mango showers: Pre-monsoon showers in Kerala and Karnataka that help the ripening of mangoes and the coffee crop.
• Andhi: Dust storms in Uttar Pradesh and Punjab.
• Western Disturbances: Low-pressure systems that start in the Mediterranean region and bring winter rain and snow to north-west India, which is useful for the rabi crops such as wheat.

Jet Streams, El Nino, La Nina and the Indian Ocean Dipole

Jet streams are fast, narrow winds in the upper atmosphere. In winter, the sub-tropical westerly jet stream flows south of the Himalaya and steers the western disturbances. In summer, it shifts north of the Himalaya, which helps the sudden "burst" of the monsoon. The tropical easterly jet stream in summer also helps the monsoon. El Nino is the warming of the surface water of the central and eastern Pacific Ocean, which weakens the Indian monsoon and often causes a drought. La Nina is the cooling of the same region and generally supports a strong monsoon. The Indian Ocean Dipole (IOD) is the difference of the sea surface temperature between the western and eastern Indian Ocean: a positive IOD tends to help the monsoon, and a negative IOD tends to hurt it. The IMD uses all these signals in its forecast.

Tropical Cyclones in India

Tropical cyclones form over the warm ocean waters (above about 26.5 degrees Celsius) with low pressure, high humidity and the Coriolis force. India is hit mostly in the pre-monsoon (April to May) and post-monsoon (October to December) seasons. The Bay of Bengal produces more cyclones than the Arabian Sea, and the east coast, especially Odisha, Andhra Pradesh and Tamil Nadu, is more exposed. The India Meteorological Department (IMD) works as one of the Regional Specialised Meteorological Centres for the North Indian Ocean and gives the names to the cyclones from a list prepared by the countries of the region.

Rainfall Distribution and Climatic Regions

The average rainfall of India is about 118 cm, but it varies from over 1,000 cm at Mawsynram in Meghalaya (one of the wettest places on earth) to less than 10 cm in parts of Rajasthan. The areas of heavy rainfall (over 200 cm) are the Western Ghats, the north-east and the Himalayan foothills. Moderate rainfall (100 to 200 cm) falls in the Ganga plain and the east coast, and low rainfall (below 50 cm) falls in the rain-shadow regions of the Deccan, Gujarat and Rajasthan. The Koeppen classification divides India into several climatic types such as the tropical monsoon (Am), tropical savanna (Aw), semi-arid steppe (BShw), arid desert (BWhw), humid sub-tropical with dry winter (Cwg) and the mountain climate (Dfc and E).

Heat Waves and Cold Waves

The IMD declares a heat wave when the maximum temperature reaches at least 40 degrees Celsius in the plains and 30 degrees in the hills, and it is a certain number of degrees above the normal. The severe heat waves of recent years have affected health, power demand and agriculture. A cold wave is declared when the minimum temperature falls to 10 degrees or below in the plains, along with a specified departure from the normal. For the Mains, link these events with the climate change and the role of the urban heat islands, and mention the heat action plans of the cities such as Ahmedabad.

Climate and Agriculture

The climate decides the cropping pattern. The kharif crops (rice, cotton, maize, sugarcane) depend on the south-west monsoon, and the rabi crops (wheat, gram, mustard) depend on the winter temperature and the western disturbances. A delayed or weak monsoon can cause a drought, which raises food prices. A good understanding of the climate also helps in the study of our notes on the Indian Agriculture and Green Revolution and Soils of India.

Climate Change and the Indian Climate: The Mains Angle

For the Mains, you must be able to discuss how climate change is altering the Indian climate. Evidence includes the rise in the average temperature, more frequent and intense heat waves, the changing monsoon pattern with long dry spells and short extreme rainfall events, the melting of the Himalayan glaciers, the sea-level rise on the coast and the more intense cyclones in the Arabian Sea. The effects are serious for agriculture, water security, health and the cities. The response includes the National Action Plan on Climate Change with its eight missions, the early warning systems of the IMD, the heat action plans, the crop insurance and the climate-smart agriculture. Mention also the international aspect, such as the Paris Agreement and India's Nationally Determined Contributions. A strong answer gives causes, effects, the government steps and the way forward in a balanced manner.

Memory Tips and Common Mistakes

• Remember "WD for winter, SW for the summer rain": the Western Disturbances give the winter rain and the south-west monsoon gives the summer rain.
• The Coromandel Coast gets most of its rain in the north-east monsoon, not in the south-west monsoon, because it lies in the rain-shadow of the Western Ghats during the summer.
• El Nino is not a cyclone. It is a warming of the sea surface that affects the global climate.
• Do not confuse the monsoon onset (around 1 June in Kerala) with the monsoon withdrawal (from north-west India in September).

Previous-Year Style Practice

• Which winds bring winter rain in north-west India? Answer: The Western Disturbances.
• Which phenomenon in the Pacific is linked to a weak Indian monsoon? Answer: El Nino.
• Which sea produces more cyclones near India? Answer: The Bay of Bengal.
• Which place has the highest average annual rainfall in India? Answer: Mawsynram (Meghalaya).

Frequently Asked Questions (FAQ)

How many seasons are there in India?

The Indian Meteorological Department recognises four seasons: winter, summer, south-west monsoon and retreating monsoon.

What are Western Disturbances?

They are low-pressure systems from the Mediterranean region that bring winter rain and snow to north-west India.

Why are Western Disturbances important?

They give winter rainfall that is very useful for the wheat crop.

What is El Nino?

It is the unusual warming of the surface waters of the central and eastern Pacific, which usually weakens the Indian monsoon.

What is the Indian Ocean Dipole?

It is the difference in the sea surface temperature between the western and eastern Indian Ocean, which affects the monsoon.

Which sea has more cyclones, the Bay of Bengal or the Arabian Sea?

The Bay of Bengal has more cyclones.

When do cyclones mostly hit India?

In the pre-monsoon (April to May) and the post-monsoon (October to December) seasons.

What is the Loo?

A hot and dry wind blowing in the north-western plains in the summer.

Where is the highest rainfall in India recorded?

At Mawsynram and Cherrapunji in Meghalaya.

What is the average annual rainfall of India?

About 118 cm.

What are mango showers?

Pre-monsoon showers in Kerala and Karnataka, which help the mango and coffee crops.

How is climate asked in UPSC?

As the concept-based questions on winds, seasons, jet streams, El Nino and cyclones, and in the Mains linked with agriculture and disasters.