•
•
•
•
•
•
•
Why October brings the monsoon's retreat, what 'withdrawal' means scientifically, and what follows for South India
India's southwest monsoon delivers the bulk of the country's annual rainfall between June and September. By late September and October, it begins its retreat, known as monsoon withdrawal. This transition shapes the end of the kharif harvest, the start of rabi sowing, festival weather and the onset of South India's northeast monsoon.
In 2020, the India Meteorological Department (IMD) revised the normal monsoon dates using newer data:
| Event | Normal date |
|---|---|
| Onset over Kerala | June 1 |
| Covers entire country | July 8 |
| Withdrawal begins from northwest India | September 17 |
| Withdrawal complete from the entire country | October 15 |
Actual dates vary considerably from year to year. In recent years, the withdrawal has sometimes started late, with extended rainfall into October in parts of central and western India.
IMD declares withdrawal from a region when atmospheric conditions show the monsoon circulation has ended. Criteria used for the start of withdrawal from northwest India include:
IMD then tracks the withdrawal line as it moves southward and eastward across the country.
The period of transition, sometimes called the "retreating monsoon", often brings hot and humid days ("October heat") interspersed with thunderstorms.
As the southwest monsoon retreats, winds reverse direction. From October to December, northeasterly winds bring the northeast monsoon rains to:
Cyclones forming in the Bay of Bengal during October–December can bring very heavy rain and strong winds to the east coast.
Scientists have observed that rainfall is becoming more erratic, with fewer moderate rain days and more extreme downpours. Several studies link changes in onset and withdrawal timing to warming oceans and shifting circulation patterns, though year-to-year natural variability remains large. Phenomena such as El Niño, La Niña and the Indian Ocean Dipole strongly influence each season.
Withdrawal normally begins from northwest India around September 17 and completes around October 15.
Because of the northeast monsoon, when winds reverse and bring moisture from the Bay of Bengal.
Not necessarily for the whole season, but it can extend rainfall in some regions into October.
Monsoon withdrawal marks one of the most important seasonal shifts in India's weather. Understanding IMD's criteria and the arrival of the northeast monsoon helps farmers, planners and residents prepare for the months ahead.
