The minimum temperature slid to 14.4° Celsius in Calcutta on Sunday, the lowest so far this season.
The Met office said the slide was not because of northwesterly winds but because the day temperature was abnormally low the day before.
“There was not enough sunlight on Saturday, which causes insulation, during the day. That is why the night temperature also dropped,” said a Met official.
The next couple of days are likely to see the day temperature rise to around 25°C, and the minimum is expected to be between 15 and 16°C, said the Met official.
“There is no immediate chance of any sharp drop in the night temperature in the next few days,” he said.
On December 6, the Met office recorded a minimum of 14.5°C in Alipore.
A layer of fog persisted over Bengal on Sunday as well.
“Dense fog was observed at one or two places over Cooch Behar district of North Bengal; shallow to moderate fog was observed at one or two places over East Midnapore, Calcutta, North 24-Parganas, Birbhum and West Burdwan districts of south Bengal and Jalpaiguri, Malda and Darjeeling districts of north Bengal,” said a Met report.
At 10.7°C, Sriniketan in Birbhum was the coldest place in south Bengal. In the hills, Darjeeling saw a minimum of 5°C.
The northwesterly winds, the usual agents of chill in Calcutta, are still relatively weak. Northerlies and easterlies are still dominant in different layers of the atmosphere.
Sunday was brighter than Saturday but still far from bright enough.
On Saturday, a fog cover that overstayed its usual tenure for hours, caused a
sharp slide in the day temperature.
The Met office recorded a maximum temperature of 20.7° C in Alipore, more than five degrees under the normal maximum temperature. On Sunday, the maximum rose to around 22°C.