Calcutta, Dec. 26: If the cold tied you to the bed this morning, you weren’t the only one.

The mercury dipped to 11.9 degrees Celsius at dawn, making it the second coldest December day in a decade.

Yesterday, Calcutta had experienced the decade’s coldest Christmas.

With conditions persistently chilly and windy, meteorologists expect the minimum temperature to go below 10 degrees “in another week or so”. At the airport, it was 10.5 degrees Celsius this morning.

“The drop in the mercury has been brought about by the absence of low-pressure formations over Bay of Bengal, which has lowered the air’s moisture content,” said an official of the India Meteorological Department, Delhi.

The only other occasion December temperature went below 12 degrees Celsius this decade was on December 31, 2007, when the minimum touched 11.4 degrees.

“The low humidity level has allowed heat to readily escape from the surface and cleared the way for the cold, dry wind from the northwest,” the Met official said.

The residue of a western disturbance (cool, moisture-laden winds from the Mediterranean) is active across eastern India now. “Another western disturbance is likely to sweep through the region next week, cooling it further,” said a scientist at the National Centre for Medium Range Weather Forecasting, Noida.

A nine-day warm spell since December 12, triggered by the sudden formation of cyclone Ward over southwest Bay of Bengal, has been followed by a steady drop in temperatures. “The minimum can come down to 10 degrees by Wednesday. But that is not a certainty,” the Noida scientist said.