Tuesday, the coldest day in the first week of December in over a decade, should set the tone for a winter 'colder and longer' than previous years.
The Alipore Meteorological Office crowned December 6 the coldest day of the season, with the mercury dipping to 13.3 degrees Celsius, two degrees below normal.
This, they added, was the 'lowest for the first week of December' in the past decade.
Officials said the cold conditions of the winter had set in rather early this year. 'Since November 15, the minimum temperature almost every day has been lower than the previous year,' said G.C. Debnath, director of the weather section at the Regional Meteorological Centre in Alipore.
The average minimum temperature at this time of the year is 15 degrees Celsius.
Debnath said the minimum temperature had dipped on Tuesday because of the clear sky and free inflow of wind from the north-western part of the country that was caught in the grips of a cold wave.
'Punjab, Haryana and parts of Rajasthan are experiencing a cold wave and this has had an impact on the Calcutta weather,' he stated.
But the weather office was quick to add that a slight rise in the minimum temperature could be expected in the next couple of days due to a trough of low pressure that has started to develop. It stretches from sub-Himalayan Bengal across Nagaland, Manipur, Mizoram and Tripura.
'Due to this development, moisture is being sucked in from the Bay of Bengal, raising the temperature slightly. We expect the minimum temperature to remain between 14 degrees and 15 degrees Celsius during the next 48 hours. On Wednesday, we expect the minimum temperature to rise to 14 degrees. However, this phenomenon is temporary,' clarified Debnath.
Once the trough of low pressure shifts or dissipates, the Celsius will slide down again.
'We feel once the sky clears and the passage opens up for the North Wind, Calcutta will experience lower temperatures than what was recorded last winter,' an official said.
The wind from the north is blowing at a speed of around 15 km per hour.
Officials said another reason why the minimum temperature was unlikely to plummet below 13 degrees Celsius just now was because it had stopped snowing in Kashmir.
Met officials also pointed out a depression that had formed over the Bay of Bengal on Tuesday, about 1,400 km south of Calcutta.
'The depression has the potential to intensify further and the system is now heading towards Tamil Nadu and Andhra Pradesh. When the system moves closer to the land it may lead to formation of clouds over Calcutta and its neighbourhood,' said Debnath.
From the present movement of the depression, Met officials added, it was unlikely to have a direct impact on the chill factor in Calcutta and the rest of Bengal.