Kolkata recorded its wettest day in nearly four decades this week, with 251 mm of rain in 24 hours, flooding streets and killing at least 10 people, mostly due to electrocution. Nearly 98 mm fell in a single hour, overwhelming the city’s aging drainage system.

The deluge was triggered by a low-pressure system over the Bay of Bengal, but scientists say warming oceans made it worse. Higher sea surface temperatures fuel more evaporation, loading the atmosphere with moisture and making extreme downpours more likely.

A simultaneous high tide in the Hooghly River prevented stormwater from being discharged, while clogged drains and silt buildup worsened waterlogging.

Experts warn Kolkata’s low-lying geography and fragile infrastructure leave it highly exposed as climate change drives heavier, more frequent rains and rising seas. The event underscores the urgent need for drainage upgrades and stronger climate resilience.