The humidity level in the atmosphere is gradually on the rise in Kolkata, compounding the agony caused by the ongoing heat spell.
When the Met office announced a heat wave alert on Wednesday, the minimum relative humidity — a measure of the moisture content in the atmosphere during the driest part of the day — had dipped sharply.
On Thursday, the minimum relative humidity was 16 per cent, making it the driest April day in at least five years.
But since Saturday, the moisture level has been on the rise. More moisture means more discomfort because of sweating.
Saturday night was especially uncomfortable. There was not a hint of breeze and people sweated profusely even after the sun went down. The minimum relative humidity was 45 per cent.
On Sunday, the minimum relative humidity was around 25 per cent, a climbdown from Saturday but the conditions were still uncomfortable.
The increased moisture content has led to a rise in the minimum temperature.
Sunday’s minimum was 29.6 degrees, compared to the usual of around 25 degrees this time of the year.
“The moisture content is leading to the formation of some clouds. But those are scattered. The clouds are taking shape in the second half of the day, by which time the temperature had clocked the day's highest. The clouds are not letting the trapped heat leave the earth’s surface. As a result, there seems to be no relief from the sultry conditions even during the evening or the night,” said Sanjib Bandyopadhyay, deputy director-general, India Meteorological Department, Kolkata.
Around 1.30pm on Sunday, the website of AccuWeather, the US-based weather forecasting agency, showed a temperature of 39 degrees and a RealFeel of 44 per cent.
The maximum temperature on Sunday climbed marginally to 39.8 degrees, four notches above normal, from Saturday’s 39.2.
“Some southerly winds are present in the lower levels of the atmosphere. The higher levels are still dominated by northwesterly winds. The conditions are still not suitable for thunderstorm activities in the immediate future. But a rise in the moisture level is always encouraging for the formation of thunderclouds as sufficient heating is already there,” said Bandyopadhyay.