NEW DELHI: The Indian Meteorological Department (IMD) has announced that the Southwest Monsoon is expected to arrive on May 26, 2026, with a model error margin of plus or minus four days. In 2025, the monsoon reached Kerala on May 24.
Earlier forecasts by the IMD indicated that the 2026 southwest monsoon season, extending from June to September, is likely to remain below normal at 92% of the long-term average, with a plus-or-minus 5% error margin. This is among the lowest forecasts issued in recent years.
Usually, the monsoon reaches the Kerala coast by June 1. The IMD’s forecast is based on an advanced statistical model developed in India. Last year, the predicted onset date for monsoons was May 27, but it arrived three days early, on May 24.
The IMD noted that its operational forecasts for monsoon onset over Kerala between 2005 and 2025 have generally remained accurate, except in 2015. The advance of the monsoon is expected to provide relief from extreme summer temperatures across several regions.
According to the IMD daily bulletin, “Conditions are favorable for the advance of the southwest monsoon over parts of the south Bay of Bengal, the Andaman Sea, and the Andaman and Nicobar Islands within the next 24 hours.”
The IMD’s prediction is based on six indicators, which include minimum temperatures over northwest India, the peak of pre-monsoon rainfall over the south peninsula, outgoing longwave radiation over the South China Sea and the southwest Pacific region, and lower tropospheric zonal winds over the southeastern Indian Ocean and the northeastern Indian Ocean.
Amid prediction of deficient rainfall, the LPA for seasonal rainfall across the country is based on data from 1971 to 2020, which amounts to 870 mm. This year, anticipated rainfall is expected to be around 800 mm.
The low rainfall forecast is primarily attributed to the emergence of strong El Niño conditions. The El Niño-Southern Oscillation (ENSO) is a natural climatic phenomenon characterized by abnormal warming in the Central and Eastern Pacific Ocean.
El Niño is often associated with a weaker and more erratic monsoon in India.
As per the IMD, since 1951, there have been 16 recorded El Niño years, of which only six contradicted the expectations of a weaker monsoon. Out of the 10 years that recorded deficient or below-normal rainfall, the patterns were consistent with El Niño effects.
Additionally, reduced snow cover in the Northern Hemisphere over the last three months has also contributed to the expectations of a weaker monsoon. Last year, India experienced above-normal monsoon rainfall, with the season concluding at 108% of expected levels.
Furthermore, a private weather agency, Skymet, has also predicted below-normal rainfall at 94% of the LPA.
