The India Meteorological Department (IMD) has forecast that the southwest monsoon is expected to arrive in Kerala on 27 May, slightly earlier than the typical onset date of 1 June.
If the monsoon arrives as predicted, it would be the earliest onset over the Indian mainland since 2009, when it arrived on 23 May, according to IMD data.
The onset of the southwest monsoon over the Indian mainland begins with its arrival in Kerala, signalling a shift from the hot, dry season to the rainy season. It typically sets in around 1 June, with a margin of ±7 days, and brings much-needed relief from the intense summer heat as it progresses northwards.
Over the past five years, the monsoon has arrived early on two occasions—2022 and 2024. In both years, the onset occurred on 29 May and 30 May, respectively, according to IMD records.
In 2024, the southwest monsoon brought rainfall at a four-year high, with around 108% of the Long Period Average (LPA), totalling 934.8 mm compared to the LPA of 868.6 mm. The IMD had forecast above-normal rainfall for the season, predicting 106% of the LPA.
For 2025, the IMD has predicted that southwest monsoon rainfall (from June to September) is likely to be above normal, exceeding 104% of the Long Period Average for the country.
Meanwhile, the southwest monsoon has further advanced over more parts of the southern Arabian Sea, Maldives and the Comorin area, the southern Bay of Bengal, remaining parts of the Andaman Islands, and parts of the east-central Bay of Bengal.
According to the IMD, conditions are favourable for further advancement of the southwest monsoon over additional parts of the southern Arabian Sea, Maldives and Comorin area, southern Bay of Bengal, central Bay of Bengal, and parts of the north-eastern Bay of Bengal during the next three to four days.
The southwest monsoon typically begins to retreat from north-west India around 17 September and fully withdraws by 15 October.
In its April forecast, the IMD predicted above-normal cumulative rainfall for the 2025 monsoon season, dismissing concerns about the potential impact of El Niño, which is generally associated with reduced rainfall in the Indian subcontinent.
The southwest monsoon is vital for India’s agricultural sector, sustaining the livelihoods of approximately 42% of the population.
Additionally, the monsoon plays a critical role in replenishing reservoirs, which are essential for drinking water and power generation across the country.
(By arrangement with livemint.com)
