The Met has forecast heavy rain in Calcutta on Saturday following the formation of a low-pressure system over the Bay of Bengal.
Darkness descended on Calcutta on Friday afternoon and rain came soon after as the system took shape.
The system prompted the Met office to issue an "enhanced-rainfall alert".
"A low-pressure area lies over northeast and adjoining east-central Bay of Bengal.... It is likely to become a well-marked low-pressure area and move northwestwards towards north Odisha and adjoining Bengal coasts during the next 48 hours. Enhanced rainfall activity likely to occur from September 29 to October over the districts of Bengal," said the bulletin.
The bulletin has predicted "heavy to very heavy rain" in East Midnapore, West Midnapore and Jhargram on Saturday. Calcutta, South 24-Parganas, Howrah, Hooghly, East Burdwan, Bankura and Purulia are likely to get heavy rain, it said.
On Sunday, Murshidabad, Birbhum, East Burdwan and West Burdwan are likely to get heavy rain.
The sky in south Bengal is expected to start clearing from Monday. But the districts of north Bengal are likely to get heavy rain from Monday, said the Met forecast.
The clouds and rain dragged the Celsius down and brought a much-needed relief from the twin assault of heat and humidity on Calcuttans over the past few days.
The Celsius had remained on the higher side for the past few days in Calcutta but Wednesday was extremely uncomfortable.