Alipore: Winter got into the Christmas spirit with a minimum temperature of 14.3 degrees Celsius, but Calcutta's coldest day of the season barely lasted the morning.

"The lowest reading was at 5.30am, after which the temperature shot up because of clear skies and increased solar radiation being absorbed by the lower atmosphere," said Ganesh Kumar Das, director of the India Meteorological Department, Calcutta.

The drop in temperature was triggered by the northwesterly wind making a comeback after around a week.

The weather office said 14.3 degrees was "normal" for this time of the year, which explains why you possibly did not feel the cold any time during the day. When the minimum temperature is 12 or 13 degrees Celsius, the flow of the northwesterly is stronger and that also keeps the maximum temperature in check.

A colder phase has been forecast from mid-week, although meteorologists aren't sure of how much the temperature will drop. "There is a Western Disturbance (an extra-tropical storm) over Uttar Pradesh that will pass over Sikkim on Tuesday. From Thursday, we expect a dip in the minimum temperature," Das said.

Monday was technically the coldest December 25 in Calcutta in three years. Last Christmas, the minimum temperature was 17.1 degrees. The previous Christmas was even warmer at 18.1 degrees.