It’s only been a week, but this June has already scored high in pre-monsoon rainfall.

Week 1 has seen more than 80mm of rain in Alipore, which serves as the official record-keeper for Calcutta.

The usual arrival date for the southwest monsoon in south Bengal is June 10. In the past five years, only 2020 saw more rain in Calcutta from June 1 to 10 (see chart).

But the southwest monsoon does not always set foot in Calcutta on June 10. In the past three years, it has made a delayed entry.

The Met office recorded 40.5mm of rain in Alipore between 8.30pm on Friday and 8.30am on Saturday. Most of it was between 10pm and midnight.

Readings at the pumping stations of the Kolkata Municipal Corporation showed parts of EM Bypass, near Dhapa, got 77mm of rain. Maniktala got 53mm, Ballygunge got 44mm and Topsia got 55mm.

In Met parlance, more than 60mm in 24 hours qualifies as heavy.

Some parts of central Calcutta, in Bowbazar and adjoining areas, had ankle-deep water on Saturday morning.

“The heat and pent-up humidity led to the formation of thunderclouds. As the clouds moved towards the coastal areas, the high moisture in the atmosphere made them stronger,” said a Met
official.

“Calcutta and its neighbouring regions got maximum rain on Friday night,” the official said.

The showers dragged the minimum temperature down.

The Met office recorded a minimum of 22.6 degrees Celsius, down five notches from usual, in Alipore. The maximum was just under 34 degrees, 1.5 degrees below
average. But the high humidity quotient meant there was little respite as the day
progressed.

The minimum relative humidity was a staggering 65 per cent. Around 2pm, the temperature was 33.5 degrees, but the RealFeel was 42 degrees.

The northern line of monsoon now passes through Balurghat in south Dinajpur.

Between June 13 and 19, a system is expected to take shape over the Bay of Bengal, triggering widespread rain in south Bengal.

“The imminent system can also propel the south-
west monsoon into south Bengal. But it is still too early to say anything,” said the Met official.