The city spent one of its hottest January days in recent years on Wednesday.
The minimum temperature soared to 20.2 degrees Celsius, five notches above normal, as heavy moisture incursion blocked the flow of northwesterly winds.
A day ago, it was 16 degrees. Two days ago, it was 13.6 degrees.
“A seven-degree jump in 48 hours is unusual. It happened because of a combination of direct sunlight and moisture incursion,” said G.K. Das, director, India Meteorological Department, Kolkata.
Dum Dum, Salt Lake, and some adjoining areas of Kolkata received some rain on Tuesday night. Kalyani in Nadia, north of Kolkata, received more than 60mm of rain, considered heavy in Met parlance, said an official.
The moisture in the air made it heavy. As a result, the air above the surface could not rise. The heat that the city received during the day got trapped and could not escape. That is why the minimum temperature shot up.
The minimum relative humidity, a marker of the moisture in the atmosphere during the driest part of the day, was 64 per cent.
In the afternoon, many on the streets of Kolkata were seen taking their warm clothes off. Outside Victoria Memorial and the Alipore zoo, hat sellers did brisk business as visitors sought some shield from the overhead sun.
Rain skipped the city on Wednesday but some showers are likely in the next two days, according to the Met forecast.
“A cyclonic circulation persists over Bangladesh. Under its impact, a trough of low pressure extends from Bangladesh to Odisha, across Gangetic Bengal. The clouds moved north of Kolkata on Wednesday. But on Thursday and Friday, they are likely to reach Kolkata and trigger some rain,” Das said.
The showers and clouds may drag the minimum temperature marginally down in the coming days, he said.
“Partly cloudy sky with one or two spells of light rain/thundershower. Maximum and minimum temperatures
most likely be around 26 degrees and 19 degrees, respectively,” read the forecast for Thursday.