Kolkata experienced a massive rainfall of 251.4 mm on the night of September 22–23, 2025, bringing the city to a halt. This event is ranked as the third-highest single-day rainfall in Kolkata’s September history, following 369.6 mm in 1978 and 259.5 mm in 1986. It is also the sixth-highest single-day rainfall overall for the city. The heavy rains led to severe flooding, waterlogging in many areas, and tragically claimed the lives of at least seven people due to electrocution.
What Caused the Heavy Rain?
The intense downpour was triggered by a low-pressure area that formed on September 22 over the northeast Bay of Bengal. This system moved towards coastal Gangetic West Bengal and neighboring regions, creating strong moisture convergence over Kolkata. The clouds reached heights of 5 to 7 km, which contributed to the heavy rain. Despite the heavy hourly rainfall peak of 98 mm, the India Meteorological Department (IMD) confirmed it did not qualify as a cloudburst, which requires rainfall exceeding 100 mm in an hour.
Impact on Kolkata
The flooding was described by Kolkata Mayor Firhad Hakim as unprecedented in recent memory, with many areas, including normally well-drained neighborhoods near the canalized Adiganga river, overwhelmed by floodwaters. The overflowing river blocked natural water drainage, worsening the situation. Several schools have been converted into shelters for those displaced by the floods, with authorities providing food and aid. The Mayor expressed hope that the floodwaters would recede quickly if no new rainfall occurs.
Weather Warnings and Future Outlook
The IMD has issued warnings about the low-pressure system’s persistence until September 24, followed by the likelihood of another low-pressure area forming around September 25 in the Bay of Bengal. This next system could intensify into a depression and move toward the Odisha and Andhra Pradesh coasts by September 27. The weather department has advised fishermen not to venture into the sea along the West Bengal and Odisha coasts until September 27 due to rough sea conditions caused by squally winds reaching 40-60 kmph.
Residents have also been cautioned to avoid shelter under trees or electric poles and stay alert for lightning strikes during this unsettled weather. The IMD expects light to moderate rains with isolated heavy showers in several South Bengal districts over the coming days, urging people to take necessary precautions.
