The minimum temperature dipped to 18.2 degrees Celsius in Calcutta on Tuesday, the lowest so far this season.

Sightings of an additional layer of clothing were reported from across the city after sundown, especially on those riding two-wheelers.

The minimum temperature in Calcutta was three degrees lower than usual. At 28.6 degrees, the maximum was also a couple of degrees lower than usual. The day felt reasonably pleasant because the maximum was also on the lower side. A minimum relative humidity of 41 per cent was the key to the slide in the Celsius.

The districts were colder. A couple of stations in Birbhum recorded a minimum of close to 14 degrees Celsius, the coldest in south Bengal. In the north, Darjeeling recorded a temperature of 9.2 degrees Celsius.

“In Calcutta, real winter means mid-December to mid-January. The city and the rest of south Bengal are in the middle of a cold and dry phase. But there is no guarantee that this will be uninterrupted. For the next five to six days at least, there is no forecast of rain,” said an official.

A marginal slide from here is not ruled out, the official said.

Without any impending system or possibility of a rise in moisture incursion over the next five to six days, the hint of chill is likely to persist, according to the forecast.

The free flow of cold and dry northwesterly winds is behind the slide in the Celsius. The Celsius is already on a downward spiral across swathes of northern and mainland India.

“Cold wave to severe cold wave conditions prevailed over some parts of West Madhya Pradesh; isolated parts of East Madhya Pradesh and cold wave conditions in isolated pockets of Haryana and Chhattisgarh,” said a Met report.

“For the next few days, the minimum is likely to remain between 17 and 19 degrees in Calcutta. The maximum is expected to stay between 28 and 30 degrees,” said the Met official.