The southwest monsoon made an early arrival in Kerala today, eight days ahead of its typical onset date of June 1, the India Meteorological Department (IMD) reported. This marks the earliest onset over the Indian mainland since 2009, when the monsoon began on May 23. While June 1 is generally regarded as the standard date for monsoon onset in Kerala, the IMD has observed growing variability in recent years. The current early onset is linked to the formation of a low-pressure area and the progressing monsoon system, which has already triggered heavy rainfall in parts of the state.

This early start is particularly noteworthy given the historical range of onset dates, with the earliest ever recorded on May 11, 1918, and the most delayed on June 18, 1972. Over the last 25 years, the latest arrival occurred in 2016, when the monsoon began on June 9.

The IMD has issued a red alert for multiple districts in Kerala, warning of extremely heavy rainfall exceeding 204.4 mm in 24 hours. Kannur and Kasaragod are under alert for May 24, while Malappuram, Kozhikode, Wayanad, Kannur, and Kasaragod will be on red alert on May 25. An orange alert was already in effect on May 23 for Thrissur, Malappuram, Kozhikode, Wayanad, Kannur, and Kasaragod, cautioning residents of heavy rain and thunderstorms.

Apart from Kerala, the monsoon system is expected to bring scattered rain and thunderstorms to Tamil Nadu, Telangana, and Andhra Pradesh over the next five days. The weather department also forecasts the monsoon to move eastward, crossing the south Konkan coast between Ratnagiri and Dapoli as a depression, which is likely to intensify rainfall in those regions.

The IMD determines the monsoon onset based on specific criteria, including rainfall data from 14 designated stations, wind direction, and cloud cover. If over 60% of these stations report at least 2.5 mm of rain for two consecutive days, accompanied by favourable wind patterns and low Outgoing Longwave Radiation, the monsoon is officially declared to have begun on the second day. This year’s onset met all those requirements, underscoring the complex and shifting patterns of India’s monsoon system.