The India Meteorological Department (IMD) on Saturday said that the monsoon had reached Kerala, the earliest since 2009. Within a day, weather experts predicted the southwest monsoon would move towards Maharashtra. On Monday morning, after a heavy downpour, the IMD declared the monsoon onset in Mumbai and upgraded the yellow alert to a red alert.
The early arrival of the monsoon, or what can be termed unseasonal rains with thunderstorms and lightning, made life uneasy for Mumbaikars in the early hours of Monday, as waterlogging on roads and railway tracks disrupted traffic on both transport facilities, leading to traffic jams. As per the data, the monsoon arrived early this year in Mumbai and broke the record for the earliest monsoon onset date, which was previously logged on May 29 — in the years 1971, 1962, and 1956. It broke a 107-year-old record. The city's routine monsoon onset date is June 11. This year’s arrival was over two weeks ahead of schedule.
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Why Did the Monsoon Arrive Early in Mumbai This Year?
The 2025 monsoon in Mumbai arrived 10 days early, just days after the onset of the monsoon was announced in Kerala. The predicted date for the onset of the monsoon in Kerala was June 1. The southwest monsoon typically moves to Maharashtra by June 6 and then reaches the Mumbai coast by June 11. However, this year, the normal pattern of the monsoon was thrown off as it travelled from Kerala to Maharashtra within 24 hours instead of the routine six-day timeline.
Shubhangi Bhute, director of IMD Mumbai, said that the early onset of the monsoon across Kerala and its fast progression were spurred by the ‘very favourable’ conditions for monsoon onset. “We observed that the atmospheric conditions were satisfying all the parameters and criteria on the basis of which onset is declared,” Bhute told The Indian Express on Sunday.
According to weather experts, early monsoon factors originated due to the currently active Madden-Julian Oscillation (MJO). A complex ocean-atmospheric phenomenon, the MJO is one of the most important factors influencing Indian monsoons.
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The MJO originated in the Indian Ocean, and a key feature is the disturbance of clouds, wind, and pressure that moves eastward at a speed of 4–8 metres per second. As per the Express report, MJO wind bands can travel across the globe and can cause significant weather changes during their movement. In a favourable phase, it can enhance rainfall over India during the monsoon season.
Furthermore, a low-pressure area in the Arabian Sea, which developed owing to cyclonic circulation, also aided the fast movement of the southwest monsoon, IMD scientists said. This low-pressure area had brought heavy pre-monsoon showers to Mumbai over the past few weeks.