The first pre-monsoon showers of the season dragged the mercury down at least seven notches in the city, bringing relief from a swelter spell.

The cooling effect was felt all over the city. The temperature dropped from around 34 degrees Celsius at 4pm to 25.3 degrees in Ballygunge, post-shower.

In Ultadanga, the Celsius slid from 33.6 degrees Celsius to 26.6 degrees.

Rain lashed parts of eastern Calcutta, including the area around the Ruby rotary, Chowbagha, EM Bypass, Esplanade, large areas of Ballygunge, Ultadanga and New Market around 4.30pm.

Ballygunge recorded 28.9mm of rainfall and New Market clocked 24.3mm. The showers lasted for almost 40 minutes.

Parts of western Calcutta, including Behala and Joka, received scant showers.

The rainfall was caused by the formation of thunderclouds because of moisture incursion from the Bay of Bengal, weather officials said.

Dark clouds had started hovering over some parts of east and central Calcutta since afternoon but the cloud formation was mostly localised.

Unlike summer rain, Tuesday’s showers were not accompanied by gusts of wind. That is a characteristic of pre-monsoon showers, officials in the Met department said.

The monsoon is expected to hit coastal south Bengal and Calcutta in another three to four days, according to the Met office. It has already arrived in north Bengal.

But a sultry spell — because of high relative humidity — is likely to precede the advent of the monsoon.

Tuesday, though, brought a much-awaited relief.

“It had been unbearable for the past two days and we just loved today’s showers,” said Sagnik Das, a businessman from Sodepur who had come to New Market with his family for shopping.

The highest temperature of the day was 38.7 degrees Celsius around 11am.

Calcutta police said there was no waterlogging but traffic slowed down along the Bypass and the Rashbehari Avenue connector during the evening rush hour.