India is entering the final month of the southwest monsoon with two important signals in view: a strong El Niño over the tropical Pacific and an official September outlook tilted towards less rain and warmer conditions.
The India Meteorological Department outlook issued on 31 August 2026 says rainfall across the country as a whole is most likely to be below normal in September. It also expects average maximum and minimum temperatures to be above normal across most of India.
That is a reason to watch conditions closely, but it is not a guarantee that every state or district will have a dry month. El Niño changes the odds. It does not provide a city-level rainfall forecast, and a monthly average cannot show exactly when rain will arrive.
What IMD expects in September
IMD classifies below-normal all-India rainfall for September as less than 91% of the long-period average. That historical average, calculated from 1971 to 2020, is about 167.9 millimetres for the country as a whole.
The national figure should not be read as a uniform forecast. IMD says many parts of India are likely to receive below-normal rainfall, while some areas in northwest, northeast, east, east-central and southeast peninsular India could receive normal to above-normal rainfall. Its maps also contain areas where the model does not show a clear signal.
Temperatures are expected to lean warmer more widely. Average maximum temperatures are likely to be above normal across most of the country. Average minimum temperatures are also expected to be above normal in most places, although parts of northwest, west-central and northeast India could see normal to below-normal minimum temperatures.
Taken together, the outlook points to an increased chance of a drier and warmer September at the national level, with important regional exceptions.
Why El Niño matters to India
El Niño is a recurring warming of the central and eastern equatorial Pacific Ocean that develops together with changes in the atmosphere. Those changes can shift large-scale wind and rainfall patterns around the tropics. In parts of South Asia, El Niño is often associated with weaker monsoon rainfall.
IMD has described El Niño as an important influence on year-to-year monsoon variability. Its explanation of the physical mechanisms affecting the monsoon says El Niño is generally associated with deficient rainfall over India, but also stresses that there is no one-to-one relationship.
The present Pacific event is strengthening. In its 13 August 2026 diagnostic discussion, the US National Oceanic and Atmospheric Administration said there was a greater than 90% chance of a very strong El Niño during the Northern Hemisphere autumn and winter of 2026-27.
That probability describes the expected strength of the Pacific event. It is not a 90% forecast of drought, a rainfall deficit or any other specific outcome in India. NOAA also notes that stronger El Niño conditions make characteristic impacts more likely, but do not guarantee them.
Why El Niño is not a verdict on the monsoon
India's monsoon responds to several interacting oceanic and atmospheric influences. El Niño is important, but it is not the only one.
IMD's historical table of rainfall during El Niño years shows how much outcomes can vary. The strong 1997 El Niño coincided with all-India June-to-September rainfall close to the long-period average, while several other El Niño years had substantial deficits. No past year provides a ready-made template for 2026.
Conditions in the Indian Ocean are another factor. IMD says the Indian Ocean Dipole is currently neutral. Its own coupled forecast system expects neutral conditions to continue through September, while some international climate centres indicate that a positive phase could develop. That uncertainty is one reason the monsoon cannot be explained through El Niño alone.
Shorter-term weather systems and week-to-week changes also shape where rain falls. A seasonal climate signal provides background risk, while local forecasts provide the more immediate picture.
What regional variation means for readers
A below-normal all-India month does not mean every part of the country will receive less rain. Some areas can finish September near or above their usual total even if the national average is below normal.
The reverse is also important. A monthly rainfall category does not describe timing, so a place can experience a wet spell within an otherwise dry month. District forecasts, impact-based warnings and extended-range updates remain more useful for immediate local decisions than the national category alone.
For Chennai and Tamil Nadu, the mention of possible normal to above-normal rainfall in some parts of southeast peninsular India should not be converted into a city-specific prediction. IMD says it will publish its October rainfall and temperature outlook, along with the October-to-December Northeast Monsoon outlook, towards the end of September 2026. That will be an important next update for Tamil Nadu readers.
What to watch next
- IMD's weekly extended-range forecasts and daily district-level forecasts, which can show how the national outlook is developing locally.
- NOAA's next ENSO diagnostic discussion, scheduled for 10 September 2026, for an updated assessment of the Pacific event.
- Updates on the Indian Ocean Dipole, where forecast centres currently differ on whether neutral conditions will persist.
- IMD's late-September Northeast Monsoon and October outlooks, particularly for southern peninsular India.
The clearest reading is that El Niño adds weight to the risk of a dry finish to the southwest monsoon and a warmer September across much of India. It still does not decide the outcome everywhere. The national outlook sets the context, while regional and shorter-range forecasts show what individual places may experience.
