The Retreating Monsoon Explained

The retreating monsoon is the gradual withdrawal of the southwest monsoon from India in autumn, normally beginning from west Rajasthan around 17 September and finishing across the country by about 15 October, as winds reverse and the rain belt shifts south. The period is also called the transition season or, in school textbooks, the season of the retreating monsoon, and it leads directly into the northeast monsoon over Tamil Nadu and the south-east coast. This explainer was last updated on 30 October 2026.

The retreating monsoon does not mean the rain ends everywhere at once. The monsoon withdraws region by region, moving from the north-west towards the south, while the skies clear, nights turn cooler and days stay warm and humid. In the south-east, the same period brings heavy rain as the winter monsoon begins, and over the Bay of Bengal it is a peak time for cyclones.

Key Takeaways

• The retreating monsoon is the withdrawal of the southwest monsoon, which normally begins from west Rajasthan around 17 September and ends by about 15 October.
• The IMD declares the retreating monsoon over a region only after rainfall has stopped for five days, the lower atmosphere has an anticyclonic flow, and moisture has fallen sharply.
• The retreating monsoon happens because the sun moves south after the September equinox, weakening the heat low over north India and reversing the surface winds.
• While the southwest monsoon withdraws from the north, the northeast monsoon begins over Tamil Nadu and the south-east coast, bringing heavy rain.
• The retreating monsoon period is a main cyclone season for the Bay of Bengal, and storms in October and November have struck Odisha, Andhra Pradesh and Tamil Nadu.
• In recent decades the retreating monsoon has often started later than the old normal date, which led the IMD to revise the normal start of withdrawal from 1 September to 17 September.

What Is the Retreating Monsoon?

The retreating monsoon is the stage of the monsoon cycle in which the southwest monsoon weakens and withdraws from the Indian mainland, usually from mid-September through October. The term describes the monsoon’s withdrawal, which moves in the opposite direction to its advance in June.

In the advance, the rain moves from Kerala northward and westward. In the retreat, the southwest monsoon flow withdraws from the north-west first, then from the Gangetic plain and central India, and finally from the peninsula. The southwesterly winds are replaced by drier northerly and northeasterly winds. Weather offices therefore describe the monsoon as “withdrawing” from the area, rather than as ending.

The period is often called a transition season because it connects two very different circulations. The humid, rainy southwest monsoon gives way to the cooler, drier winter pattern, with the northeast monsoon rains arriving in the south-east on the way.

Why Does the Monsoon Retreat?

The monsoon retreats because the sun’s overhead position moves south of the equator after the September equinox, ending the intense heating of the Indian landmass that drives the monsoon winds. As the land cools, the heat low over north India fills in, and the pressure pattern that pulled moist air from the ocean no longer holds.

The main steps in the process are:

• Southward shift of the sun: After around 23 September, the sun is overhead south of the equator, and the northern hemisphere receives less direct sunlight each day.
• Weakening of the monsoon trough: The trough of low pressure over the Gangetic plain weakens and shifts south and east towards the Bay of Bengal.
• Southward movement of the ITCZ: The Intertropical Convergence Zone, the equatorial belt of rising air and cloud, moves back south, taking the heavy rain with it.
• Build-up of high pressure: A cold, dry high-pressure area builds over the continent, and an anticyclone develops in the lower atmosphere over north-west India.
• Wind reversal: The southwesterly winds weaken and are replaced by northerly and northeasterly flow over most of the country.

How Does the IMD Declare the Withdrawal of the Monsoon?

The IMD declares the withdrawal of the monsoon from an area when three conditions are met together: a break in rainfall, a shift in the winds, and a drop in moisture. These objective criteria stop the declaration from being based on a short dry spell.

1. Rainfall: The area has had no rain for five consecutive days.
2. Anticyclone: An anticyclonic circulation is established in the lower troposphere, around the 850 hectopascal level and below, which means descending, stable air.
3. Moisture: Satellite water vapour images show a considerable reduction in the moisture content of the air.

Once these are met over a region, the IMD announces that the southwest monsoon has withdrawn from it and publishes the new “southern limit of withdrawal” on its daily maps. Until the monsoon has fully withdrawn, the line steadily shifts south, and the IMD declares the monsoon’s withdrawal from the whole country when it has left the southern peninsula.

When Does the Retreating Monsoon Start and End?

The retreating monsoon normally starts around 17 September from west Rajasthan and ends around 15 October, though the dates vary by weeks from year to year. The IMD revised the normal start date a few years ago to reflect the later withdrawals seen in recent decades, shifting the normal start of withdrawal from 1 September to 17 September while the normal completion date stays near 15 October.

The timing varies considerably. In 2019, for example, the withdrawal began on 9 October, among the latest start dates in IMD records, after a very wet and prolonged season. Other years have seen withdrawal start in the third week of September or even earlier. The delays are partly a result of the Bay of Bengal producing low-pressure systems in September that keep the rain going over central and eastern India.

What Is the Weather Like During the Retreating Monsoon?

The weather during the retreating monsoon is typically clear in the north and central India, with warm days, cooler nights and a noticeable fall in humidity, while the south-east becomes rainy. The change often feels like a short, uncomfortable second summer before the real cool season of winter.

• Clearer skies: The anticyclone brings descending air, which suppresses cloud formation and gives bright sunshine.
• Rising day temperatures: With the sun still high in the sky and little cloud, day temperatures rise, and the heat feels worse with the leftover humidity. This spell is often called “October heat”.
• Falling night temperatures: Clear nights lose heat rapidly, so mornings become cooler.
• Thunderstorms and local showers: Isolated showers continue in some places, especially in the east, where lows from the Bay of Bengal keep the moisture alive.
• Wind shift: Winds turn to northerly or northeasterly, and the coastal breezes change character.

In many northern cities, the calm, dry air of this period also traps pollutants near the ground. The season of crop-residue burning in parts of Punjab and Haryana overlaps with the calm autumn weather, and air quality tends to deteriorate in the weeks after the monsoon leaves.

How Is the Retreating Monsoon Connected to the Northeast Monsoon?

The retreating monsoon is directly connected to the northeast monsoon because the withdrawal of the southwest monsoon from the south creates the conditions for the winter monsoon to set in over Tamil Nadu and the south-east coast. The two events are often announced together by the IMD.

As the southwest monsoon withdraws and the winds turn northeasterly, the air crosses the Bay of Bengal, gathers moisture and meets the east-facing coast of the peninsula. The result is rainfall that peaks in October to December. Tamil Nadu receives close to half of its annual rain in this season, while coastal Andhra Pradesh, south interior Karnataka and parts of Kerala also receive a good share.

The rain in the south-east at this time is often described as “the retreating monsoon rain” in textbooks, even though modern meteorology treats it as a separate system, the northeast monsoon. Both descriptions point to the same physical change, which is the reversal of the wind from the southwest to the northeast.

Why Is the Retreating Monsoon a Cyclone Season?

The retreating monsoon is a cyclone season because the Bay of Bengal remains warm after summer, the winds aloft become favourable, and low-pressure systems form easily over the sea. October to December is the second of the two annual cyclone seasons in the North Indian Ocean, the first being April to June.

Many of the most destructive Indian cyclones have occurred during this period:

• The Odisha super cyclone of October 1999, one of the strongest ever recorded in the region.
• Cyclone Phailin in October 2013, which led to a large evacuation along the Odisha and Andhra Pradesh coasts.
• Cyclone Hudhud in October 2014, which struck Visakhapatnam.
• Cyclone Titli in October 2018 over Odisha and Andhra Pradesh.
• Cyclone Gaja in November 2018 over Tamil Nadu.

These storms bring strong winds, storm surge and heavy rain to the east coast. Improved forecasting by the IMD and better evacuation planning have sharply reduced loss of life compared with earlier decades, but property damage and flooding remain serious risks.

How Does the Retreating Monsoon Affect Farming and Daily Life?

The retreating monsoon affects farming by determining the final rain that reaches standing kharif crops and the soil moisture available for the following rabi sowing. A smooth, timely withdrawal allows harvesting and drying of crops such as rice, cotton and soybean, while late rain can damage mature crops in the field.

• Kharif harvest: Dry, sunny weather helps with threshing and drying, but unseasonal rain in October can spoil grain and cotton.
• Rabi sowing: Moisture left in the soil after the monsoon supports sowing of wheat, mustard, gram and other winter crops.
• Reservoirs: The final inflows of the season decide how much water is stored for the dry months ahead.
• Health: Mosquito-borne diseases such as dengue often peak in the weeks after the rain, since stagnant water lingers while the weather stays warm.
• Festivals and travel: A late withdrawal can disrupt festival celebrations, travel and outdoor events in October.

How Is Climate Change Affecting the Retreating Monsoon?

Climate change is linked with later and more irregular withdrawals of the monsoon, together with more intense late-season rain, according to the IMD’s observations and several research studies. The IMD’s decision to push back the normal withdrawal dates is itself a recognition that the monsoon has been staying longer in recent decades.

A warmer Bay of Bengal and Arabian Sea can provide more moisture and energy to low-pressure systems in September and October. This can prolong the rain in central and eastern India, and also strengthen post-monsoon cyclones. The result may be heavier rain in the wrong season, with crops standing in the field and rivers already full.

Researchers stress that year-to-year differences remain large, and not every late withdrawal can be blamed on warming. Even so, the trend has practical meaning for farmers, who now need flexible sowing and harvesting plans, and for cities that must prepare drains and flood defences well into October.

Bottom Line

The retreating monsoon is the orderly withdrawal of the southwest monsoon from India, moving from the north-west to the south between mid-September and mid-October. It brings clear skies and October heat to the north, but also cyclones to the Bay of Bengal and the start of the northeast monsoon rains over Tamil Nadu.

Frequently Asked Questions

What is the retreating monsoon?

The retreating monsoon is the withdrawal of the southwest monsoon from India in autumn. It moves from the north-west to the south between about mid-September and mid-October.

When does the monsoon withdraw from India?

The monsoon normally begins to withdraw from west Rajasthan around 17 September and leaves the whole country by about 15 October. The IMD moved the normal start date from 1 September to 17 September to reflect later withdrawals in recent decades.

How does the IMD decide that the monsoon has withdrawn?

The IMD declares withdrawal when an area has had no rain for five consecutive days, an anticyclone has set in over the lower atmosphere, and satellite images show a clear drop in moisture. All three conditions must be met together.

Why does Tamil Nadu get rain when the monsoon is retreating?

Tamil Nadu gets rain during the retreat because the northeast monsoon begins as the winds reverse. Northeasterly winds cross the Bay of Bengal, pick up moisture and rain on the east-facing coast from October to December.

Why is October so hot and humid after the monsoon?

October is hot and humid after the monsoon because the sun is still high, skies are clearer, and plenty of moisture remains in the air and soil. The spell is often called October heat and lasts until the cooler winter air arrives.

Are cyclones common during the retreating monsoon?

Yes, October to December is the main post-monsoon cyclone season in the Bay of Bengal. Warm seas and favourable winds let low-pressure systems intensify into cyclones that often strike Odisha, Andhra Pradesh and Tamil Nadu.

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