A warm bundle of joy at Alipore zoo. (Pradip Sanyal)

Winter is finally here, and it’s here to stay, says the weatherman.

Hazy Thursday was the coldest day of the season with the minimum temperature dropping to 15.2 degrees Celsius, one point above normal.

Last week, the city had witnessed record December temperature highs with the mercury shooting up to eight degrees above normal last Friday.

The tide has turned this week and the mercury will now slide down steadily, said the Alipore Meteorological office.

“The conditions are favourable for winter. The anti-cyclonic activity over central India, which was blocking the North Wind blowing into Bengal, has receded,” said Asish Kumar Sen, the director of the Alipore Met office.

“The phenomenon started over the weekend and the temperature took a dip almost at once. It will go down further over the next couple of days,” he added.

If the days have appeared more chilly than the nights, the weathermen points to the cloud cover that has narrowed the gap between the maximum and minimum temperatures. This might persist for a couple of days.

“The low cloud formation has blocked the sun’s rays that cause heat by radiation. As a result, the city remained cooler than usual till noon,” explained Sen.

The maximum temperature on Thursday was 20.5 degrees Celsius, six degrees below normal. The maximum temperature on the same date last year was 32.7 degrees Celsius.

A global weather forecast has suggested that this winter could be the severest since 1998, but the Alipore weather office chose not to make any predictions.

“A pattern that has emerged since 2006 indicates that winter gets delayed because of low-pressure formations and cyclonic disturbances. The same happened this year but there isn’t a forecast on the intensity of winter,” said Sen.

The most obvious harbinger of winter this week has been the fog cover that grounded flights and slowed down trains from Monday.

The hardest hit has been the Calcutta airport, with flight schedules going haywire and the mercury of stranded passengers rising with every haze-filled hour.

With many passengers booked on morning flights now opting to travel in the evening, there is a scramble among the airlines to provide special measures for fog-hit fliers. These range from sending text messages to passengers to providing delay-linked refreshments at the airport.

“Passengers are requested to provide their personal contact numbers while booking, to ensure that they can be reached with updated flight information should there be any delay due to fog,” said Sanjay Aggarwal, the chief executive officer of SpiceJet.

For delays in excess of two hours, the low-cost airline will give passengers a refreshment voucher, redeemable at the airport counters. Passengers are being advised to carry toiletries and other essentials in case the flight is diverted for a night halt.

“Additional manpower will be deployed to assist passengers needing information and special assistance,” said a spokesperson for Air India.

Jet Airways is trying to ensure that one flight delayed does not mean several flights being disrupted. “We have an extra 175-seater aircraft parked at Calcutta airport to try and make up for lost time,” said an official.