Calcuttans can brace for the coldest winter in the city’s recorded meteorological history, with the minimum temperature on Monday plummeting to 10.8 degrees Celsius, three points below normal.

At the airport the minimum temperature was 9.3 degrees Celsius.

“Calcutta has experienced colder days in January — the coldest being January 14, 1989, when the mercury slid to 8.4 degrees Celsius — but a sub-11 minimum temperature in December is unprecedented,” said an official at the Delhi-based India Meteorological Department (IMD).

A senior scientist at the Noida-based National Centre for Medium Range Weather Forecasting said: “If there are no adverse atmospheric formations, the minimum temperature in the next few weeks may drop below 8 degrees, making this winter the coldest in Calcutta’s recorded Met history.”

The cold spell started soon after the dissipation of the residue of Cyclone Ward off the Tamil Nadu coast, with the minimum temperature dropping eight degrees in eight days, from 18.8 on December 20 to 10.8 on Monday.

Weather watchers attribute the sharp drop to the fall in the humidity level — the minimum mark on Monday being 28 per cent — allowing free flow of northwesterlies and western disturbances.

“A second factor behind the unusual chill is the frequent occurrence of western disturbances, more intense and south-bound than in previous years,” said O.P. Sharma, the chief meteorologist of a private weather agency.

Meteorologists said the western disturbances — cold, moisture-laden winds from the Mediterranean — this year had been colder than usual because of climate changes over the Mediterranean Sea.

“The surface temperature of the Mediterranean is much lower and the sea rougher this winter. The western disturbances, as a result, are colder and more potent,” said a climate analyst attached to an independent agency.

The western disturbances, the expert added, is resulting in a cold wave condition across Punjab, Haryana and Uttar Pradesh. In Punjab’s Adampur, the minimum temperature plunged to minus 1 degree Celsius.

Officials in the Regional Meteorological Centre at Alipore said the sky on Tuesday was likely to remain clear.

The minimum temperature is likely to hover around the 10-degree mark, setting the stage for the coldest New Year’s Eve in Met memory.