Friday was the coldest day this season, with the mercury dipping to 15 degrees Celsius, a notch below normal.

The weatherman predicted that the temperature would dip further by a couple of degrees over the weekend.

“Minimum temperatures are below normal by up to three degrees across east India and Calcutta is no exception,” said an official of the India Meteorological Department in Pune.

“Minimum temperatures are likely to dip by about two degrees Celsius over many parts of east India, including Calcutta and its neighbourhood, over the next couple of days,” the official added.

The city had experienced a similar plunge of the November mercury on November 30, 2005 (14.9) and November 16, 1999 (14.3).

Temperatures are going to slide steadily from next week and the minimum temperature could be as low as 13 degrees Celsius soon, said the weatherman.

Independent meteorologists attributed the increased chill to the weakening of a low pressure area over the Bay of Bengal and the free flow of northwesterlies.

“The low-pressure area over the Bay of Bengal, which kept temperatures in Calcutta above normal this week, has weakened considerably. Also, the cold, dry northwesterlies are blowing in freely across south Bengal, resulting in a drop in temperature,” said O.P. Sharma, the chief meteorologist of a private agency.