The city was lashed with the heaviest showers in more than a month on Monday, the rain starting in the afternoon and continuing in spells throughout the evening and into the night.

More rain is likely over the next 48 hours. “Heavy rain is expected in Calcutta, and North and South 24-Parganas on Wednesday. The two Midnapores and the western districts of Bengal are also likely to get heavy rain,” said an official at the Alipore Met office.

“The intensity of the showers is likely to reduce from Wednesday.”

A strong monsoon current and a cyclonic circulation over Andhra Pradesh together triggered Tuesday’s showers, the weather department official said.

With the sky remaining overcast, darkness descended on Chowringhee around 2.30pm. The 42, the city’s tallest residential tower coming up along JL Nehru Road, was shrouded in a haze of dark clouds. On Red Road and other thoroughfares, cars plied with their headlights switched on.

By evening, traffic crawled on several roads because of waterlogging. Snarls were reported from the Parama flyover, AJC Bose Road flyover, CR Avenue, Amherst Street, Dum Dum underpass and Bidhan Sarani, police said.

“There is a cyclonic circulation over Andhra Pradesh and neighbouring areas, extending up to 3.6km above the mean sea level, tilting southwards.... The monsoon current is very active over Gangetic Bengal, leading to heavy incursion of southerly winds from the sea,” said Sanjib Bandyopadhyay, deputy director-general, India Meteorological Department, Calcutta.

Till 9.30pm, Dhapa was the wettest area in Calcutta on Tuesday, recording 77mm of rain. Cossipore received 62mm and Behala 57mm.

The last time the city got heavy rain was on August 16 and 17, under the impact of a cyclonic circulation. The first two weeks of September saw several days of rain, none heavy.

In Met parlance, 60-120mm of rain in 24 hours qualifies as heavy rain.

The first 14 days of September received close to 190mm of rain. The next nine days received only around 50mm.