The mercury has been pushing 38 degrees but the heat is unusually dry this time.

The moisture content in the atmosphere has been on the lower side for several days now. The minimum relative humidity — a marker of the moisture content in the air during the driest part of the day — had been hovering under 30 degrees till Tuesday (see chart).

As a result, people are sweating comparatively lesser than they do when the Celsius goes past 37 degrees.

“The usual minimum relative humidity in March-end is over 40 per cent. But this year, it has been unusually low,” said a Met official.

He attributed the low humidity to “lack of winds from the Bay of Bengal”.

Another impact of the low moisture content has been the absence of local thunderstorms.

A traffic police officer tries to beat the heat by splashing water on his face and drinking some at Esplanade on Wednesday. Gautam Bose

The high heat and humidity content towards the end of March usually combine to trigger a few spells of thunderstorms in the evenings. The pent-up heat leads to the formation of rain-bearing clouds. But this time, the city has not seen any thunderstorm so far. That could change from the weekend, the Met office has said.

“The dry heat is expected to persist till Friday. There could be some winds from the Bay from Saturday. There is a possibility of thunderstorm activities towards the evening from Sunday,” the Met official said.

“Calcutta is also expected to be under the grip of a pressure gradient during the weekend, which could see winds blowing at 30kmph and above in the city,” said the official.

In a statement issued on Wednesday, the Met office at Alipore has dismissed reports on social media about “a tropical cyclone likely to form over the Bay of Bengal in the end of March”.

“As of now, there is no such possibility,” said an IMD official.