Kolkata, 23 Sept

At least 10 people were killed, nine of them from electrocution, as torrential overnight rain - among the heaviest in four decades - left Kolkata and adjoining districts paralysed on Tuesday, disrupting air, rail and road transport, shutting educational institutions, and prompting the state government to advance Puja holidays.

The deluge - 251.4 mm in less than 24 hours - was the highest since 1986 and sixth-highest single-day rainfall in the last 137 years, only behind the record 369.6 mm in 1978, 253 mm in 1888, and 259.5, 98 years later.

This threw flight operations into chaos with more than 90 cancellations and over 90 delays reported till evening, even as waterlogging paralysed normal life across the metropolis.

Between midnight and 7.30 pm on Tuesday, as many as 42 incoming and 49 outgoing flights were cancelled at Netaji Subhas Chandra Bose International Airport due to incessant downpour, restricted visibility and poor weather at both Kolkata and outstation destinations, an AOCC (Airport Operations Control Centre) bulletin said.

In addition, 33 arrivals and 62 departures were delayed, while at least one flight had to be diverted, the bulletin said.

The aviation chaos mirrored the citywide disruption as Kolkata lay waterlogged under record rainfall.

Vehicles remained stranded on arterial roads, Metro serviceswere suspended on waterlogged stretches of the Blue Line, and thousands of commuters were left to wade through waist-deep water in several neighbourhoods.

Kolkata Municipal Corporation (KMC) sources said the southern and eastern parts of the city were worst hit, with Garia recording 332 mm of rainfall within a few hours and Jodhpur Park 285 mm.

The India Meteorological Department (IMD) has warned of more heavy showers in southern and eastern districts of West Bengal over the next 24 hours, attributing the spell to a low-pressure system over the northeast Bay of Bengal.