The days this winter have been the coldest in at least a decade.
The stretch between December 15 and January 15 is considered the peak winter period in south Bengal.
In 2025-26, the chill was sharper and more persistent than usual. The average daily maximum temperature during this 31-day period stood at 23.1° Celsius — more than two degrees below normal and the lowest in at least a decade (see chart).
While minimum temperatures are used to describe how cold a night has been, but maximum temperatures offer a better measure of how cold a day feels, as their impact lasts longer and is more palpable.
This winter, the daytime chill was striking. Between December 15 and January 15, only one day — January 11 — recorded a maximum temperature above normal, and that too by a fraction of a degree. On the remaining 30 days,
the mercury failed to reach the average mark.
The mean daily minimum temperature during this period was 14.1° Celsius, making it the second lowest in a decade.
The 30-year average minimum temperature for Calcutta is 15.5° in December and 14.3° in January. The corresponding average maximum temperatures are 26.7°and 25.5°.
Past winters underline how cold this season has been. Between December 15, 2018, and January 15, 2019, the mean daily minimum temperature was lower at 13.8°, but the mean daily maximum was much higher at 25.6°.
The winter of 2019-20 was similar to this one: the average daily minimum between December 15 and January 15 was 14.1°, but the mean daily maximum was higher at 23.7°.
Why so cold?
The prolonged chill was the result of a combination of factors. During the day, dense fog and persistent low-level clouds often hid the sun for hours, preventing surface heating. These clouds frequently lingered longer than expected, dragging down daytime temperatures.
At night, the cold was driven by the uninterrupted flow of dry northwesterly winds. Winters in Calcutta are usually marked by alternating cold and warm spells, with brief rises in temperature often triggered by Western Disturbances.
Although several Western Disturbances formed this year as well, none were strong enough to block the northwesterly winds over south Bengal. Most moved towards Tibet and China along the upper reaches of the country. Only one system, in the first week of January, caused snowfall in Sandakphu in north Bengal and in Sikkim. In south Bengal, it caused only a marginal rise in temperature.
The lowest minimum temperature in Calcutta this season was 10.2° on January 6.
Forecast
The Met office has forecast a rise in temperatures next week. “A fresh Western Disturbance is expected to emerge over northwest India on January 19. As it moves from west to east, it is likely to weaken the flow of dry and cold northwesterly winds,” said a Met official at Alipore.
The rise, however, is not expected to be sharp. “The maximum temperature may increase to around 26° and the minimum to around 16°. The hint of chill will still be there, especially after sunset,” the official said.
The Met office has also not ruled out the possibility of another dip in temperatures.