Although the arrival date does not correlate with the amount of precipitation, the latter is a cause for concern this year. Archive | Photo credit: Nirmal Harindran.
Revising the forecast for the onset of the southwest monsoon over Kerala, where the weather system makes landfall on the Indian mainland, the India Meteorological Department said on Tuesday (June 2, 2026) that the rainy season was now “likely to begin” around Thursday, June 4.
On May 15, the IMD predicted onset over Kerala on May 26, with a model error of plus or minus four days. A June 4 arrival exceeds even the upper limit of that window, May 30. It is the first time since 2015 (when a May 30 forecast gave way to a June 5 start) that the department has failed to correctly call the arrival of the monsoon in Kerala. The IMD’s operational start forecasts, which are based on a customized forecast model, had been accurate every year from 2005 to 2025, except for that gap.
The IMD said conditions as of Monday (June 1) “are favorable for further advance of southwest monsoon towards some more parts of southwest and southeast Arabian Sea, Lakshadweep Islands, some parts of Kerala and Tamil Nadu and Bay of Bengal around June 4.” An upper-air cyclonic circulation off the southern coast of Kerala is expected to contribute to that final push. The IMD forecast isolated heavy to very heavy rain over Kerala for the next six to seven days.
The IMD placed the northern boundary of the monsoon (the system’s cloud headland) along a line running from 10°N/60°E across the southern Bay of Bengal to 22°N/97°E as of Monday (June 1), and the rain has yet to cross over to the Kerala mainland.
Pre-monsoon rains flood Mumbai, waterlogging slows traffic in some areas
The IMD declares the onset of monsoon over Kerala on any day after May 10, when at least 60% of the 14 designated stations across the state and adjoining coast (including Thiruvananthapuram, Kochi, Kozhikode and Mangaluru) record 2.5 mm or more rainfall for two consecutive days. Two other conditions must be met: westerly winds must extend to about 600 hPa (about 4.5 km) over the southeast Arabian Sea, and outgoing longwave radiation must fall below 200 W/m², an indicator of the deep cloud and convection that differentiates the monsoon from mere rain.
IMD officials have said The Hindu that the system had stalled near the coast instead of weakening. The slip comes with a season already forecast to be below normal, 90% of the long-term average, under an El Niño phenomenon.
Published – June 02, 2026 12:39 pm IST
