The city had a nearly perfect January day on Thursday, marred only by the polluted air. The morning was warm and pleasant, while the night was cold.

The minimum temperature at Alipore was 11.6 degrees, up from 10.3 degrees the day before. At 21.9 degrees, the maximum was almost similar to Wednesday (22°C).

Both temperatures were more than a couple of degrees lower than usual.

Commuters on a motorbike wrapped in woollens in Esplanade on Thursday afternoon

“No large change in minimum temperature (night temperature) during the next 2 days; thereafter a slight rise by 2°C during the subsequent 2 days over the districts of south Bengal,” said a Met bulletin on Thursday.

In Calcutta, the minimum may climb up to 13 degrees by the weekend, about normal for this time of the year, said a Met official. He did not discount the possibility of a fresh slide in the Celsius next week.

Shallow to moderate fog is likely at several places in south Bengal, including Calcutta, on Friday, according to the forecast. In north Bengal, the fog is likely to be dense.

Northwesterly/northerly winds at lower tropospheric levels are likely to prevail over West Bengal. Dry weather is very likely to prevail over all districts during the next seven days.

A depression over the deep sea intensified into a deep depression on Thursday. Around 5.30am, some 400km from Hambantota in Sri Lanka, the Met office said. “It is very likely to cross the Lankan coast between Hambantota and Kalmunai on Friday night. The system has no direct impact on Bengal,” said a Met official.

Air quality remained a concern on Thursday, also. At 11am, one station (Ballygunge) reported “very poor” air quality, four reported “poor”, and two reported “moderate” air quality. At 4pm, there was only marginal improvement. Five stations reported “very poor” air quality while two reported “moderate” air quality.

The air quality at any point in time is an average of the air quality of the previous 24 hours.