August ended with 560mm of rain, registering a 160 per cent surplus, after huge deficits in June and July. August’s normal count is 345mm.

Met officials attributed the surplus rain to a string of rain-triggering systems that formed over the Bay of Bengal in August, something that was missing in the preceding months.

The cumulative monsoon deficit for Calcutta stood at 20 per cent on August 30. At the end of July, it was around 62 per cent and at the end of June 69 per cent.

The key to the August surplus was rain throughout the month, barring seven days, according to Met office records. In comparison, July had 19 days without rain.

“A majority of the rain-bearing systems formed over the Northern or Northwestern part of the Bay, which is closer to the Odisha coast. Odisha received more rain but coastal areas of Bengal, too, receivedconsistent rain throughout August,” Sanjib Bandyopadhyay, deputy director-general, India Meteorological Department, Calcutta, said.

Friday and Saturday in the city have been hot and humid without rain. The mercury reached 34.2 degrees Celsius on Saturday, two notches above normal.

September is likely to start on a wet note, a Met official said. “Another low-pressure is likely to form over the northern Bay in the next 24-48 hours. Rain is likely from Sunday evening.”