July ended with a marginal rain deficit — around 10 per cent — in the city.

In July, usually the rainiest month, the city received 350mm of rain compared with the usual quota of around 400mm, India Meteorological Department, Calcutta, figures showed.

July 2019 was among the driest in recent memory, with 160mm of rain in the city.

The showers over the month, unlike conventional monsoon rain, were because of local thunderclouds.

The monsoon trough was stationed over the foothills of the Himalayas for most of July this year, like it had been last year. But unlike in 2019, this year the city received rain on several days because of local cloud formation.

The absence of a strong system over the Bay of Bengal, which is common in July, was behind the trough not coming south last month, said G.K. Das, director, IMD, Calcutta. A strong system pulls the trough down. When it descends, coastal Bengal receives rain. When it is over the foothills of the Himalayas, north Bengal and the Northeast get rain, he said.