India Meteorological Department (IMD) has officially announced the onset of the southwest monsoon over Mumbai on 26th May 2025, setting an all-time record for the earliest arrival of monsoon over the city. This marks a 15-day advance from the normal onset date of 15th June..
On the morning of 26th May 2025, significant rainfall was recorded at Colaba: 139.5 mm & Santacruz: 33.5 mm observed at 0830 IST. These rainfall figures further substantiated the monsoon’s arrival, supported by other synoptic observations.
Meteorological Factors Behind the Early Onset
One of the primary drivers behind this early onset was the formation of a low-pressure system over the East-Central Arabian Sea, near the North Karnataka–Goa coast. This system intensified and tracked northwards and made landfall over Ratnagiri on 24th May 2025. Later weakened into a low-pressure area over South Madhya Maharashtra.
This sequence of events intensified the monsoon westerlies and pushed the monsoon current far ahead of schedule, bypassing the usual pattern. While the monsoon was expected to make its initial advance over Kerala, it swiftly reached Karwar and surged up the Konkan coast, culminating in an early arrival over Mumbai.
Onset Dates in last two years:
2024: 06th June
2023: 25th June
Check here for more statistical Monsoon dates for last 68 years over Mumbai.
Image source IMD.