India’s Financial Capital, Mumbai, experienced a rare weather event this Monday, May 26, as the monsoon arrived nearly two weeks earlier than usual, hitting the city with full force and throwing daily life out of gear.
Several areas in the city saw heavy waterlogging, traffic jams, and slow-moving trains as the rains came pouring down in what has already become an extraordinary May for the city.
According to the India Meteorological Department (IMD), this is the earliest that monsoon has ever arrived in Mumbai since recordkeeping began in 1950.
The previous earliest date was May 29, seen in 1971, 1962 and 1956. Normally, the rains make their way to Mumbai around June 11. This year, the monsoon made an exceptionally swift journey from Kerala, where it arrived on May 24, to Maharashtra within just 24 hours, reaching Mumbai by Monday.
Madden-Julian Oscillation and other factors
This quick progression of the southwest monsoon was made possible by highly favourable atmospheric conditions. Experts say that the Madden-Julian Oscillation (MJO), a major factor that influences rainfall, played a big role.
The MJO is a moving system of winds and clouds that travels around the globe, and when it is active over the Indian Ocean, it can significantly boost rainfall across the Indian subcontinent. At the time of the monsoon’s advance, it was in a favourable phase, bringing intense rain.
Waterlogging hits BMC's own premises at Nana Chowk, Grant Road, exposing infrastructure challenges.
— Mid Day (@mid_day) May 26, 2025
Commuters faced inconvenience as rainwater flooded the area despite civic claims of preparedness.
Credits: @MNCDFbombay member Dr. @vinitgada93 #MumbaiRains #BMC #Monsoon2025… pic.twitter.com/C7WrnHEpXS
Another reason for the fast-moving monsoon was a strong cross-equatorial flow, which brings moist winds from the Southern Hemisphere to the Northern Hemisphere, along with a low-pressure area over the Arabian Sea.
This low-pressure system, which developed due to a cyclonic circulation, had already been causing heavy pre-monsoon showers in Mumbai in the past few weeks and helped the monsoon winds advance more rapidly than usual.
Wettest month in over a century
This month has now become Mumbai’s wettest May in over a century. The IMD’s Colaba station has recorded 295 mm of rainfall so far, breaking the previous record of 279.4 mm set in May 1918.
Santacruz has also received 197 mm of rain, making it the rainiest May for the suburb since 2021. These rain spells have also kept heatwaves away from the city this year. In fact, on May 8, Mumbai saw its coldest May morning in over 70 years, with temperatures dropping to 22.2 degrees Celsius.
Mumbai is not alone in witnessing this unusual weather. Across Maharashtra, districts like Buldhana have recorded a rainfall surplus of over 4,000 percent compared to their normal May rainfall. Coastal regions like Sindhudurg and Raigad have also seen excess rain, with surpluses crossing 2,600 percent and 2,000 percent respectively, as per reports
Looking ahead, Mumbai can expect a good monsoon this year. The IMD has predicted an above normal season for the entire country, with rainfall likely to be 105 percent of the long period average. Neutral conditions of El Niño Southern Oscillation and the Indian Ocean Dipole are expected to support a strong monsoon throughout the season.
