An already drenched city will have to grapple with “an increase in rainfall” on Sunday and Monday.

A low-pressure area is expected to take shape over the Bay of Bengal by Sunday evening, a Met official said. Under its impact, the intensity of the rain is likely to go up from the second half of Sunday. “The next two days are likely to see an increase in rainfall in the city. Heavy rain is not ruled out,” the Met official said.

Heavy rain in the city is much more likely if the low-pressure area forms over the north Bay, the official said. The other possibility is the Northwest Bay, in which case Odisha’s coastal areas will be more affected.

The whole city received rain on Saturday, mainly in the afternoon. A few areas in the south were more drenched.

Saturday’s rain was triggered by the monsoon trough, which now passes over Calcutta on its way to the Northeast Bay of Bengal, the Met official said. “Because of very strong monsoon currents, many thunderclouds had formed over the city. Some parts in the south had more thunderclouds.”

Some bylanes around Bansdroni market were waterlogged, residents said. Less than 3km away, stretches of Kalighat had knee-deep water in the afternoon.

For a second consecutive day, the rain coincided with high tide and water in the Adi Ganga breached banks and flooded nearby roads, a Calcutta Municipal Corporation official said.

“In August and September, when the level of the Hooghly is already above normal, rain and high tide lead to more inundation,” said the official.

Seven portable pumps had drained the water out by evening, said Tarak Singh, a member of the CMC’s board of administrators in charge of drainage.

The forecast for more rain threatens to flood more areas. Singh said there was little the civic body could do if heavy rain and high tide came together. “But the waterlogging will not persist for days. We have 650 portable pumps to drain out water from low-lying areas,” he said.