Hottest-day race hots up after respite

A child shields himself from the blazing sun with a fan near Victoria Memorial on Monday. (Pradip Sanyal)

Alipore: The record for the hottest day in two years was broken for the second time in less than a week when the maximum temperature soared to 40.6 degrees Celsius on Monday, marking a return to "heatwave-like" conditions after a Sunday respite.

The weather office expects the torment to continue longer than a day, although there is a chance of a thundershower in the next 48 hours.

"The shower, if it happens, will be localised rather than widespread rainfall typical of the monsoon," an official of the India Meteorological Department (IMD) said.

The maximum temperature was almost six degrees higher than the 34.8 recorded on Sunday and seven notches above the normal reading for this time of the year. According to AccuWeather and Google Weather, the impact of the maximum temperature outdoors was equivalent to 48 degrees Celsius.

The last time the temperature had risen to 40.6 degrees in the city was on April 12, 2016. That was in the middle of a three-day heatwave. "The same temperature seems more oppressive now than in summer because humidity is high and sweat doesn't dry easily," a weather scientist said.

On April 12, 2016, minimum relative humidity, which denotes the moisture content of air during the hottest part of the day, was 26 per cent. On Monday, minimum relative humidity was 39 per cent.

A heatwave is declared when the temperature above 40 degrees and is more than 4.5 degrees above the normal for that time of the year. The weather office hasn't declared a heatwave in Calcutta yet because the maximum temperature has not crossed 40 on two consecutive days. If the Celsius scale shows 40 degrees or more on Tuesday, the classification of Calcutta's summer agony during the monsoon will go from "heatwave-like conditions" to "heatwave".

The temperature had touched 40 degrees on Friday, but came down to 39.7 the next day before dipping further to 34.8 on Sunday after localised clouding and sporadic rainfall.

Missing monsoon

An IMD veteran said he could not remember the last time a heatwave was declared in Calcutta after the onset of the monsoon. The spell of extreme heat in central and north India has played its part in the city's plight. "It was 41.3 degrees in Lucknow and 42.2 degrees in Patna on Monday. Hot winds from these places are blowing into Calcutta," said Devendra Pradhan, the additional director general of the IMD in New Delhi.

He said the south-westerly flow of monsoon winds had almost stopped because of the absence of weather systems over the Bay of Bengal. The monsoon flow has been weak as well.


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