The Celsius can slide to 15 degrees in Calcutta by this weekend, the Met office has said.

Sunday was mostly cloudy and some parts of the city got light rain early on Monday.

A Met official attributed the clouds to a southerly component in the wind pattern linked to the remnants of Cyclone Fengal, which made landfall near Puducherry on November 30.

“In Calcutta, the conditions are likely to improve on Tuesday. The decrease in the moisture level will pave the way for the comeback of northwesterly winds. The minimum temperature will go down gradually and a five-degree fall is expected by the weekend,” said H.R. Biswas, who heads the weather section at the Regional Meteorological Centre in Alipore.

“Strong northwesterly winds can drag the Celsius to under 15 degrees as well.”

The minimum temperature on Monday was 20 degrees, more than three notches above normal. The cloudy sky, however, kept the day temperature on the lower side with a maximum of 25.6 degrees, a couple of notches below normal.

A Met bulletin on Monday said Fengal had weakened into a deep depression at 11.30am on Sunday, a depression at 5.30pm the same day and a well-marked low-pressure area at 5.30am on Monday.

Under the indirect influence of the system, southerly and southeasterly winds from the Bay entered south Bengal, leading to the formation of clouds.

“Northwesterly winds are active up to a kilometre above the surface of the earth. Southerly winds are dominating the zone from 1.5km to 3km. Northwesterly winds are again active above that zone,” said a weather scientist.

The dry and cold northwesterly winds from Kashmir bring the chill to much of mainland India during winter. The winds reach south Bengal via Punjab, Delhi, Haryana, Uttar Pradesh and Bihar. “The temperature has to go down in these places before the chill sets in here,” said Biswas.