Calcutta experienced the most sweaty and uncomfortable day of the season on Monday with moisture in the air doubling overnight and the sun beating down through a cloudless sky.
The weather office said there was a “50 per cent chance” of a thunderstorm in Calcutta on Tuesday or Wednesday, but not strong enough to provide lasting relief.
On Monday, minimum relative humidity, which indicates the presence of water vapour in the air when the day is at its hottest, rose from 18 per cent on Sunday to 38 per cent. A little before 2.30pm, the mercury hit the day’s high of 37.5 degrees Celsius, a notch above normal.
The discomfort index, which calculates the effect of these two factors on the human body, soared to 64.8 degrees Celsius, 10 rungs above normal for this time of the year.
Even on March 30, when the maximum temperature had soared six degrees above normal to the season’s highest of 39.9, the discomfort index was at 61 degrees Celsius. The key factor then was the minimum relative humidity of 28 per cent. “Even a slight rise in relative humidity increases the feeling of discomfort greatly at constant temperature,” a weather scientist said.
Those who stepped out when the sun was blazing on Monday were sapped of energy in no time. Many were taken ill.
At Chandni Chowk Metro station, a woman suddenly slumped on the stairs in the afternoon. “I sprinkled some water on her face. When she opened her eyes, I asked if she needed medical assistance. She was helped to her feet by three women accompanying her and the group boarded a taxi,” said a guard on duty at the station.
Weather maps showed a cyclonic circulation over north Bengal with a trough line along the Bay of Bengal stretching till Odisha. Had the trough formed a little to the west, chances of a Nor’wester in Calcutta would have increased, the Met office said.