India’s southwest monsoon is likely to arrive four days ahead of schedule this year, with onset over Kerala expected around May 27, the India Meteorological Department (IMD) announced on Saturday. The forecast comes with a margin of error of ±4 days.
This early arrival signals potential relief for an increasingly heat-stressed nation and holds significant implications for agriculture and the broader economy, particularly in managing inflation concerns amid global economic pressures.
“All conditions are favourable for an early onset. High night-time temperatures over northwest India are a good indicator. Our models are showing early monsoon onset,” said M Mohapatra, director general of IMD.
Satellite images already indicate dense cloud cover over the Andaman Sea and around the Kerala region. “The clouding over the region indicates monsoon onset may happen around May 13 over Andaman Sea, some parts of Bay of Bengal and Nicobar islands,” Mohapatra added.
The southwest monsoon normally begins over Kerala on June 1, with a standard deviation of about seven days. Its progression northward typically brings much-needed relief from scorching summer temperatures across the country, but the march has in recent years been staggered – leading to flooding in some regions and deficient rains in others.
IMD’s extended range forecast shows widespread rainfall expected over Kerala and the southern west coast between May 22-29 and the following week, supporting the early onset prediction.
The monsoon onset forecast relies on six key predictors: high minimum temperatures over northwest India, pre-monsoon rainfall peak over the southern peninsula, mean sea level pressure over the subtropical northwest Pacific Ocean, outgoing longwave radiation (OLR is the total radiation going to space emitted by the atmosphere, or the extent of cloudiness) over south China Sea, and wind patterns over the northeast Indian Ocean and Indonesia region.
The agency claims its operational forecasts during the past 20 years (2005-2024) have proved correct except in 2015. Recent years show varying degrees of accuracy in their predictions: In 2020, IMD forecast onset date to be June 5, but monsoon arrived on June 1. In 2023, forecast was for June 4, while monsoon made onset on June 8. In 2024, the forecast was for May 31, but monsoon arrived on May 30.
This early onset prediction follows IMD’s long-range forecast that the monsoon season — between June and September — is likely to be “above normal” at 105% of the Long Period Average, with a model error margin of ±5%. Last year, monsoon rainfall was “above normal” at 108% of LPA.
However, forecast accuracy has been mixed in recent years. In 2023, the IMD predicted “normal” monsoon rains at 96% of the LPA, but the season turned out to be below normal with 94% rain recorded—which was, to be sure, within the agency’s error margin.
It also comes at a time when northwest India has experienced an unusually cool and rainy start to May—typically the peak summer month—due to frequent, slow-moving western disturbances originating in the Mediterranean Sea, as reported by HT on May 9.
This unusual pre-monsoon weather pattern, combined with the early onset forecast, raises both hopes and concerns about the increasingly unpredictable nature of the climate amid global warming trends.
Experts said it was early to tell if the unusually cool and rainy weather ahead of monsoon onset could corrupt the monsoon rain in June.
To be sure, the rains can still falter following the onset. In Delhi, for instance, its normal date of onset is June 30.