Monsoon 2026 review: A below-normal forecast, a late onset and the withdrawal
The 2026 monsoon began late, opened weak, and is now withdrawing through the third week of September. What follows unpacks the machinery behind those headlines, from how the forecast is made to what happens once the southwest monsoon leaves.
The season in five facts
Forecast. IMD's Long Range Forecast, issued in May 2026, placed June–September rainfall at 90% of the Long Period Average, putting the season in the below-normal band.
Onset. The monsoon reached Kerala about three days later than normal.
Mid-June. Rainfall ran roughly 28% below normal, raising early concern.
Core season. July and August progressed normally.
Withdrawal. On 18 September, IMD announced conditions were becoming favourable for withdrawal from parts of West Rajasthan around 19 September.
Sources: PIB: IMD Long Range Forecast 2026 · IMD monsoon information
The mechanisms
The Long Period Average (LPA). The 1971–2020 mean monsoon rainfall for the country as a whole is 87 cm.
How rainfall is classified. Rainfall at 96–104% of the LPA counts as normal, 90–96% is below normal, and below 90% is deficient.
How onset is declared. Onset is declared when rainfall, wind and cloud conditions match the Kerala criteria in the first week of June.
How withdrawal is declared. Reduced rainfall, falling humidity and dry weather over northwest India mark the withdrawal.
The ocean drivers
The forecast's caution came from the state of two oceans.
El Niño and La Niña (Pacific). El Niño weakens the Walker circulation and delays onset, which suppresses the monsoon. La Niña does the opposite and strengthens it.
The Indian Ocean Dipole (Indian Ocean). This is the difference in sea-surface temperature between the western and eastern equatorial Indian Ocean. A positive IOD strengthens the monsoon, and can offset a neutral or weak El Niño year.
What follows
With the southwest monsoon withdrawing, the northeast monsoon takes over from October. It brings the October–December rainfall on which Tamil Nadu, coastal Andhra Pradesh and adjoining areas depend.
The simple point to remember is which monsoon feeds which coast. The southwest monsoon feeds the west coast and most of India from June. The northeast monsoon feeds the southeast coast from October.
Prelims traps
| Statement | True or False |
|---|---|
| "The LPA is the 1971–2020 average of 88 cm" | False. The 1971–2020 LPA is 87 cm |
| "Rainfall at 90% of LPA counts as normal" | False. It is below normal (90–96%) |
| "A positive IOD weakens the Indian monsoon" | False. It strengthens it |
| "Withdrawal begins from West Rajasthan" | True |
Part of: Environment and Climate, July 2024 to June 2026
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Source: India Meteorological Department; Ministry of Earth Sciences.