May 2025 did not see a single tropical cyclone on the Bay of Bengal, a first since 2020.

Amphan struck in May 2020, Yaas in May 2021, Asani in May 2022, Mocha in May 2023 and Remal in May 2024.

This year, a system on the Bay intensified into a deep depression and landed near Raidighi in South 24-Parganas’ Mathurapur on Thursday afternoon. It then drifted towards Bangladesh, sparing Calcutta and many parts of south Bengal the onslaught of heavy rain.

May 2025 was also the second-coolest in Calcutta in at least five years, according to Met records.

The average maximum temperature this May was 34.3 degrees. May 2020 saw an average maximum temperature of 34.1 degrees. The mean daily maximum temperature for May in Alipore — the official record-keeper for Calcutta — is around 35 degrees, based on Met compilations for three decades from 1981.

Last year, Calcutta and most of south Bengal had already suffered multiple heat assaults by the first week of May. May had begun amid a heatwave. The maximum temperature in Alipore on May 1 was 42 degrees. A long stint of scorching conditions was broken by a wet spell that began on May 6.

This year, the maximum temperature in Alipore knocked on the doors of 40 degrees on May 10 (39.1 degrees) and 11 (39.4 degrees).

This year, May has seen 11 days of rain. The usual is seven. The volume of rain was not much but overcast conditions kept the mercury under check.

The city, and much of south Bengal, however, stares at a period of gruelling heat, the Met forecast said. North Bengal, at the same time, will be drenched.

A trough runs from northeast Uttar Pradesh to east Vidarbha at 0.9km above mean sea level, said a Met official. It will trigger heavy rainfall in north Bengal.

“Parts of south Bengal may get localised thunderstorm activities for a day or two. But after that, there is very little chance of rainfall for the next week. In Calcutta, the day temperature is likely to go up to 36 degrees by mid next week,” said a Met official in Alipore.

On Saturday, the maximum temperature in Alipore was 33.9 degrees, up from 32 degrees the day before. The minimum relative humidity was 71 per cent. This meant the discomfort index was high throughout the day. Even in the evening, people sweated profusely.

The heat and humidity led to thunderstorms in several districts, including Howrah and Hooghly, which border Calcutta.

“The humidity will dip slightly in the coming days,” said a Met official.

The southwest monsoon entered parts of north Bengal on Thursday. But it was not
clear when it would enter south Bengal, said a Met official.

The usual date for the arrival of the monsoon in Calcutta and other parts of south Bengal is around June 10.

Last year, the monsoon reached north Bengal on May 31 but set foot in south Bengal only on June 21.