The coldest day in 13 years left Calcuttans shivering even in the afternoon.
The maximum temperature plunged to 18.2° Celsius, seven degrees below what is usual for late December. It was the lowest day temperature recorded in Alipore since December 28, 2012, when the maximum was 16.3° Celsius.
The minimum also dropped slightly to 13.5°, about normal for this time of year. Since the gap between night and day temperatures was less than five degrees, there was hardly any respite from the chill.
On Tuesday, the day temperature is expected to rise only marginally, Met officials said. The maximum is likely to be around 21° and the minimum around 13°, according to the forecast. This means the day is still going to feel much colder than usual.
A Met official said that on Monday, the day temperature was dragged down by a combination of fog and moisture incursion in the lower atmosphere, which led to the formation of low-level clouds. The sun was hidden for much of Monday morning. Even after the fog cleared, the sun hardly made its presence felt.
The night temperature dipped because of northwesterly winds, he added.
“Northeasterly winds are active in the lower levels of the atmosphere. They are coming from a cyclonic circulation over Bangladesh, via the Bay of Bengal. These moist winds led to the fog and clouds thereafter,” said H.R. Biswas, head of the Regional Meteorological Centre in Alipore.
As a result of the moisture incursion, the minimum relative humidity was 71% on Monday. Usually, when only the cold and dry northwesterly winds are active, the minimum relative humidity is below 45%.
“Northwesterly winds from the upper reaches of India are active near the surface of the earth. That is why the night temperature dropped slightly from the day before,” he said.
Winterwear stalls in New Market were busy throughout the day. Places like the Alipore zoo and Victoria Memorial also saw a decent weekday turnout. Men on the Maidan lit fires to keep themselves warm even under the sun.
Riding two-wheelers was a challenge. Many commuters were forced to book app-based bikes after a suicide bid disrupted Metro services in the evening. “It is going to be tough. But the fare on a four-wheeler is more than double,” a man told another passenger outside Chandni Chowk Metro station, as he pulled a skull cap out of his bag as an additional cover along with his helmet.
Any significant drop in night temperature is felt for a shorter time, when most people are usually asleep in their homes. In contrast, a low day temperature has a more pronounced effect because it lasts longer while people are up and out for work.