Mumbai saw a record weather phenomenon on Monday, May 26, 2025, when the city received its heaviest rainfall in more than a century on the first day of the monsoon season. The India Meteorological Department (IMD) said that the onset of monsoon happened a complete 16 days prior to schedule, which is the earliest over Mumbai in the last 75 years.
“Southwest Monsoon has proceeded towards Mumbai today, 26th May 2025, against the usual date of advance, 11th June. Hence, the monsoon has reached Mumbai 16 days ahead of schedule. This is the earliest monsoon advance over Mumbai from 2001–2025,” the IMD asserted in an official release.
Historic Rainfall Record Broken
The rain shower not only indicated the monsoon’s onset—it broke a century-and-a-half-old record. Figures with the Brihanmumbai Municipal Corporation (BMC), quoted by The Indian Express, indicate that South Mumbai localities received more than 200 mm of rain between midnight and 11 a.m. alone.
The Colaba weather station, in fact, received 295 mm of rain—beating the old record of 279.4 mm on May 1918.
According to a PTI report, regional rain gauges measured by the IMD reported the following levels from 8:30 a.m. to 11 a.m. on Monday:
- Colaba: 105.2 mm
- Santacruz: 55 mm
- Bandra: 68.5 mm
- Juhu Airport: 63.5 mm
- Chembur: 38.5 mm
- Vikhroli: 37.5 mm
- Mahalaxmi: 33.5 mm
- Sion: 53.5 mm
Monsoon Timeline Shifted
The IMD pointed out that this year’s onset of monsoon was on May 26, as against the average date of June 11. In 2024, the rain had set in on June 6.
“Southwest monsoon made onset over Mumbai on May 26. This is the earliest onset in last 75 years,” IMD scientist Sushma Nair told PTI.
Red Alerts Issued Across the Region
As the rains continued, the IMD upgraded Mumbai’s status from an ‘orange’ alert to a ‘red’ alert, indicating the likelihood of more extreme weather. Red alerts were also announced for Thane, Raigad, and Ratnagiri districts.
Simultaneously, IMD issued warnings for other states as well. “Southwest Monsoon has further penetrated into some additional areas of central Arabian Sea, some additional areas of Maharashtra including Mumbai, Karnataka including Bengaluru, remaining areas of Tamil Nadu, some areas of Telangana and Andhra Pradesh, some additional areas of westcentral & North Bay of Bengal, Remaining areas of Mizoram, entire Tripura, Manipur, Nagaland, Arunachal Pradesh, some areas of Assam and Meghalaya, on May 26,” IMD said.
