The Four Seasons of India

In the previous chapter, we looked at the grand engine of India's climate: the monsoon. We learned how the differential heating of land and water, combined with the shifting of global pressure belts, creates this massive seasonal reversal of winds. But how does this grand system actually play out on the ground, month by month, for the people living in India?

If you ask someone on the street how many seasons there are, they might say three: summer, winter, and the rainy season. If you ask a poet, they might name six traditional Indian seasons (Ritus like Vasant and Sharad). But for our purposes—and for the official records of the Indian Meteorological Department (IMD)—the Indian climate is divided into four distinct seasons.

Understanding these four seasons is not just about memorizing months. It is about understanding a continuous, year-long story. It is the story of the sun appearing to move north and south across the equator, dragging the earth's heat and rain belts along with it.

By the end of this chapter, you will understand exactly why northern India freezes while the south stays warm, why violent thunderstorms strike Bengal in May, what causes the oppressive "October Heat," and how a storm born in the Mediterranean Sea ends up watering the wheat fields of Punjab.

Let us walk through the Indian year, season by season.

The Framework: How the Sun Drives the Year

Before we dive into the specific seasons, we need to establish one fundamental rule of geography: temperature dictates pressure, and pressure dictates winds.

When land heats up, the air above it warms, expands, and rises. This creates an area of Low Pressure. When land cools down, the air above it becomes cold, dense, and heavy, sinking to the ground. This creates an area of High Pressure. Because nature hates a vacuum, winds always blow from High Pressure to Low Pressure to balance things out.

The entire cycle of Indian seasons is driven by the apparent movement of the sun:

1. 1In the winter months, the sun is shining directly over the Southern Hemisphere (the Tropic of Capricorn). India, being in the Northern Hemisphere, gets slanted, weaker sun rays. The land cools down, creating High Pressure.
2. 2In the summer months, the sun marches northward, eventually shining directly over the Tropic of Cancer, which cuts right through the middle of India. The land bakes, creating an intense Low Pressure zone.

The Indian Meteorological Department (IMD) uses this shifting pressure system to divide the year into four official seasons:

1. 1The Cold Weather Season (Winter): Mid-November to February
2. 2The Hot Weather Season (Summer): March to May
3. 3The Advancing Monsoon Season (Rainy): June to September
4. 4The Retreating Monsoon Season (Autumn): October to November

Let us explore each one in detail.

1. The Cold Weather Season (Mid-November to February)

The cold weather season sets in by mid-November in northern India and stays until February. December and January are the coldest months in the northern part of the country.

The Temperature Divide: North vs. South

During this season, there is a massive difference in temperature between North and South India.

In the North (places like Punjab, Haryana, Delhi, and Jammu & Kashmir), the temperatures drop significantly. The average daily temperature in the northern plains ranges between 10°C and 15°C, and night temperatures can easily drop below freezing in the higher altitudes of the Himalayas, resulting in heavy snowfall.

Why is the North so cold?

• Distance from the sea: The northern plains are far from the moderating influence of the ocean (a concept called continentality). Land cools down very quickly in winter.
• Snowfall: The nearby Himalayan ranges experience heavy snow, and cold winds sweep down from the mountains into the plains.

In the South (places like Kerala, Tamil Nadu, and coastal Andhra Pradesh), "winter" is just a word on the calendar. The average temperature hovers around 24°C to 25°C. Why? Because South India is close to the equator (so the sun's rays are still relatively direct) and surrounded by the ocean on three sides. The ocean retains heat and acts like a giant thermal blanket, preventing the coastal areas from ever getting truly cold.

Pressure and Winds: The Northeast Trades

Because northern India is so cold, a high-pressure region develops over the northern plains. Meanwhile, the Indian Ocean to the south is relatively warmer, creating a low-pressure area.

Following our golden rule (winds blow from High to Low), winds begin to blow from the landmass of northern India towards the Indian Ocean in the south. Because of the Earth's rotation, these winds are deflected and blow from the Northeast to the Southwest. These are known as the Northeast Trade Winds (or the Winter Monsoon).

The Exception: Winter Rain in Tamil Nadu

There is one major exception to the dry winter rule, and exams love to test this.

While the Northeast Trade Winds blow over land for most of their journey, the winds that blow over the Bay of Bengal pick up a significant amount of moisture from the sea. When these moisture-laden winds hit the eastern coast of India—specifically the Coromandel Coast (Tamil Nadu)—they are forced to rise, causing heavy rainfall.

Western Disturbances: The Winter Lifeline of the North

While the Northeast winds are dry, northern India does get a small but crucial amount of rainfall in the winter. This rain does not come from the monsoon; it comes from a fascinating weather phenomenon called Western Disturbances.

How does a storm from the Mediterranean Sea reach India? It is carried by the Subtropical Westerly Jet Stream—a fast-moving river of air high up in the atmosphere that blows from west to east.

Though the total amount of winter rainfall (locally called Mahawat) is small, it is worth its weight in gold for Indian agriculture. This gentle, steady rain is absolutely vital for the Rabi crops (winter crops) like wheat, barley, and mustard, which are grown extensively in Punjab and Haryana.

2. The Hot Weather Season (March to May)

As March arrives, the sun begins its apparent journey northward towards the Tropic of Cancer. The global heat belt shifts north, and India begins to bake.

The Rising Heat

The heating happens progressively from south to north.

• In March, the highest temperatures (around 38°C) are recorded in the Deccan Plateau.
• In April, the heat moves north into Gujarat and Madhya Pradesh, where temperatures frequently hit 42°C.
• By May, the heat belt has settled over the northwestern parts of the country. In the deserts of Rajasthan and the plains of Punjab and Haryana, temperatures can soar to a blistering 45°C to 48°C.

Falling Pressure

As the northern plains heat up like a furnace, the air above them expands and rises. By the end of May, an elongated, intense low-pressure area (a trough) develops, stretching from the Thar Desert in the northwest all the way to Patna and the Chota Nagpur plateau in the east.

This intense low pressure is the trigger that will eventually pull the monsoon winds in from the ocean. But before the monsoon arrives, this extreme heat creates violent local weather phenomena.

Local Winds of the Summer Season

The hot weather season is characterized by strong, dusty, and sometimes violent local winds. You must know the four major ones, as they are distinct to their regions and highly testable.

• The Loo: These are strong, gusty, hot, and dry winds that blow during the day over northern and northwestern India (UP, Bihar, Punjab, Haryana, Rajasthan). The Loo usually blows in May and June. It is so intensely hot that direct exposure to these winds can cause fatal heatstroke. Sometimes, the Loo continues to blow late into the night.
• Kal Baisakhi (Nor'westers): In West Bengal and Assam, the intense heat causes localized low-pressure centers that pull in moist air from the nearby Bay of Bengal. This clash of hot land air and moist sea air creates violent thunderstorms, accompanied by strong winds and torrential downpours, often with hail. Because these storms occur in the Hindu month of Baisakh (April-May) and cause massive destruction to life and property, they are called Kal Baisakhi (the calamity of the month of Baisakh). Despite the danger, these showers are actually good for the local tea, jute, and rice crops.
• Mango Showers: Towards the end of the summer season, pre-monsoon showers become common in Kerala and coastal Karnataka. They are affectionately called "Mango Showers" because this timely rain helps in the early ripening of mangoes and prevents the fruit from falling off the branches prematurely.
• Blossom Showers (Cherry Blossom): Also occurring in Kerala and nearby areas, these pre-monsoon showers are crucial for the coffee plantations, as they help the coffee flowers to blossom.

3. The Advancing Monsoon Season (June to September)

By early June, the low-pressure condition over the northern plains has become so intense that it acts like a giant vacuum cleaner. It becomes strong enough to attract the trade winds from the Southern Hemisphere.

These winds originate over the warm subtropical areas of the southern Indian Ocean. They cross the equator and, due to the Earth's rotation, are deflected to the right, blowing into the Indian peninsula from the southwest. Hence, they are known as the Southwest Monsoon Winds.

Because these winds have traveled thousands of kilometers over a warm ocean, they bring abundant moisture to the subcontinent.

The Onset and the "Burst"

The monsoon does not arrive gently. It usually arrives at the southern tip of the Indian peninsula (Kerala) by the first week of June. When it arrives, the normal weather suddenly changes. The rainfall increases suddenly and continues constantly for several days. This sudden, violent onset of rain, accompanied by thunder and lightning, is known as the "Burst" of the monsoon.

Upon hitting the wedge-shaped Indian peninsula, the Southwest Monsoon splits into two branches:

1. 1The Arabian Sea Branch: This branch hits the Western Ghats. The mountains force the moist winds to rise, causing incredibly heavy rainfall (over 250 cm) on the windward side (the western coastal plains like Mumbai and Kerala). After crossing the Ghats, the winds descend into the Deccan Plateau, losing most of their moisture, creating a "rain shadow" area (which is why places like Pune get much less rain than Mumbai). This branch then sweeps northwards towards Saurashtra, Kachchh, and eventually Rajasthan.
2. 2The Bay of Bengal Branch: This branch sweeps across the Bay of Bengal, picking up more moisture, and hits the northeastern states of India (Assam, Meghalaya) and West Bengal. The Garo, Khasi, and Jaintia hills funnel these winds upwards, resulting in some of the heaviest rainfall in the world (Mawsynram in Meghalaya holds the global record). The towering Himalayas then block these winds from crossing into Tibet, forcing them to turn west and travel up the Ganga valley, bringing rain to Bihar, UP, and eventually Punjab.

By mid-July, both branches merge over the northwestern plains, bringing the entire country under the grip of the monsoon.

"Breaks" in the Monsoon

The monsoon does not rain continuously for four months. It has wet and dry spells.

These breaks occur because the monsoon trough (the main low-pressure axis) constantly shifts its position north and south. When the trough moves south over the plains, the plains get heavy rain. When the trough shifts north closer to the Himalayas, the plains experience a dry "break," while the Himalayan foothills get torrential rain (often causing devastating floods in the plains below).

4. The Retreating Monsoon Season (October to November)

Nothing lasts forever. By October, the sun begins its apparent journey back south towards the equator and the Tropic of Capricorn.

As the sun moves south, the intense low-pressure trough over the northern plains begins to weaken. At the same time, the land starts to cool down, and high pressure begins to build. The Southwest Monsoon winds lose their strength and begin to withdraw from the country.

This withdrawal is a gradual process. The monsoon withdraws from northwestern India by early September, from the central peninsula by mid-October, and completely leaves the country by early December. This transition period is known as the Retreating Monsoon season.

October Heat

The retreat of the monsoon brings a very specific and uncomfortable type of weather.

When the rain stops and the clouds clear, the sun beats down on land that is still completely soaked with water from four months of rain. The temperature rises rapidly, but because the ground is wet, the humidity remains incredibly high.

During the day, the weather becomes sticky, sweaty, and unbearable. It is only by November, as the winter high-pressure system fully establishes itself, that the temperatures begin to drop and the weather becomes pleasant again.

Cyclones of the Bay of Bengal

While northern India is sweating through the October Heat, the eastern coast of India faces a severe threat.

As the low-pressure trough moves south from the land into the Bay of Bengal, it creates the perfect conditions for the formation of tropical cyclones. These cyclonic depressions originate over the Andaman Sea and are steered towards the eastern coast of India.

These cyclones are massive, violent storms characterized by hurricane-force winds and torrential rain. They frequently strike the deltas of the Godavari, Krishna, and Kaveri rivers (affecting Odisha, Andhra Pradesh, and Tamil Nadu). They cause immense destruction to life, property, and agriculture. Very few years pass without a major cyclone hitting the eastern coast during the retreating monsoon season.

Quick Revision

If you are reviewing this chapter right before your exam, make sure you have these high-yield facts locked in:

• The Four Seasons: Winter (Mid-Nov to Feb), Summer (March to May), Advancing Monsoon (June to Sept), Retreating Monsoon (Oct to Nov).
• Winter Rain in the North: Brought by Western Disturbances originating in the Mediterranean Sea. Crucial for Rabi crops (wheat).
• Winter Rain in the South: The Coromandel Coast (Tamil Nadu) gets its maximum rainfall in winter from the moisture-laden Northeast Trade Winds.
• The Loo: Hot, dry, dusty winds blowing over northern India in May/June.
• Kal Baisakhi: Violent, destructive pre-monsoon thunderstorms in West Bengal and Assam.
• Mango Showers: Pre-monsoon rain in Kerala/Karnataka that helps mangoes ripen.
• Monsoon Burst: The sudden, violent onset of the Southwest monsoon in early June, usually hitting Kerala first.
• October Heat: The oppressive weather in October caused by a combination of high temperature and high humidity after the monsoon withdraws.
• Autumn Cyclones: The retreating monsoon season is notorious for deadly tropical cyclones hitting the eastern coast (Odisha, Andhra, Tamil Nadu) from the Bay of Bengal.