Explained: Why Mumbai is seeing a rainy start to October
What's the story
May 26 marked Mumbai's earliest monsoon onset in 75 years. However, the city continues to receive more rain than usual, even though the month of October has begun. The India Meteorological Department (IMD) has forecast another spell of rainfall from Monday, further delaying the city's monsoon withdrawal. Normally, the southwest monsoon starts withdrawing around October 8, but this year it seems to be pushed back.
Weather patterns
What is causing unseasonal rains?
The continued rain activity in Mumbai is attributed to an approaching western disturbance. This weather system, which usually brings rain to north India in winter, originates near the Mediterranean region and travels eastward across Afghanistan and Iran, after collecting moisture from the Mediterranean, Black, Caspian, and Arabian seas. In Mumbai, this has resulted in a monsoon trough intensifying rainfall over the western coast, a long, low-pressure zone stretching from Pakistan to the Bay of Bengal.
Rain forecast
Cyclone Shakthi poses no threat to Maharashtra's coast
A senior scientist from IMD Mumbai told the Indian Express, "While the city is experiencing warm and sunny days at present, by October 6 and 7, it may get cloudy and start experiencing enhanced rainfall." This is due to a western disturbance affecting the region over the next few days. Meanwhile, Cyclone Shakhti in the Arabian Sea does not pose a threat to Maharashtra's coast as it is expected to move northwest after October 5.
Climatic shift
Why is the monsoon retreat delayed?
The IMD officially declares the withdrawal of the monsoon after observing certain conditions, like dry weather for five consecutive days, a change in wind direction, reduced moisture in the air, and a visible shift in weather patterns. This year's delay is not unusual, however, as Mumbai has seen delayed monsoon retreats for six consecutive years. In 2024, the monsoon withdrew on October 15, while in 2023 and 2022 it retreated as late as October 23.
Rainfall data
Mumbai has received more than 3,100mm of rain this season
Since the start of the monsoon in June, Mumbai has received significantly more rain than average. The Santacruz observatory has recorded over 3,100mm of rain so far, against a seasonal average of 2,319mm. This year alone, the city received 512mm in June and 798mm in July. In August and September, it received 1,184mm and 606mm, respectively.