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The India Meteorological Department (IMD) announced that the monsoon has officially begun in Kerala on Saturday, May 24, which is eight days earlier than the usual expected date of June 1. This onset signifies the start of the four-month southwest monsoon period from June to September across India, a season that delivers over 70 percent of the country’s yearly rainfall. Consequently, this date holds substantial importance in India’s economic calendar.
Stronger-than-usual cross-equatorial winds
During May, winds originating from the southern hemisphere start to sweep across the equator and enter the Arabian Sea. When these winds are more robust and organized, they propel moisture-rich air towards the Indian coast at a faster pace, accelerating the onset of the monsoon.
Above-normal sea surface temperatures
Warmer-than-average waters in the Arabian Sea and Bay of Bengal stimulate intense convection (rising air currents), which is essential for the formation of cloud bands and low-pressure systems necessary for the monsoon.
In 2025, sea surface temperatures in this region were above average, facilitating early cloud formation.
Early formation of low-pressure areas or depressions
The emergence of a low-pressure area over the Bay of Bengal or Arabian Sea can speed up monsoon winds towards the Indian subcontinent. These systems function like a magnet, attracting moisture-laden air northward.
Madden-Julian Oscillation (MJO)
This phenomenon is an eastward-moving pulse of clouds and rainfall near the equator. If the MJO phase is favorable and positioned near the Indian Ocean, it can enhance convection and rainfall activity, supporting an early onset of the monsoon.
Fading El Niño / transition to La Niña
The shift from an El Niño year to a La Niña phase typically results in stronger monsoon winds. In early 2025, global climate models suggested a weakening of El Niño and a potential development of La Niña — a trend historically linked to more vigorous and earlier monsoon seasons in India.
Pre-monsoon disturbances
Various pre-monsoon weather systems, including a likely low-pressure area anticipated to form over the Bay of Bengal by May 27, boosted early rainfall activity. These disturbances contributed to saturating the atmosphere and acted as a catalyst for the advancement of the monsoon.
(Newsroom staff only edited this story for style from a syndicated feed)
