Vast swathes of northern and eastern India will continue to experience cold to severe cold over the next three days with maximum temperatures at some places falling 6.5°C below expected normals, the national weather agency said on Friday.

Persistent cold northwesterly winds close to the surface is likely to mean severe cold day conditions in parts of Punjab, Haryana, Delhi, Chandigarh, northern Rajasthan and Uttar Pradesh and cold day conditions in parts of Uttar Pradesh, Bihar, Jharkhand, Bengal and Sikkim, the India Meteorological Department said.

The IMD, in its Friday evening forecast, also said it expects a gradual fall in the minimum temperatures by 3°C to 4°C over eastern India during the next two or three days.

For the Indo-Gangetic plains, the IMD labels days as “cold” when maximum temperature ranges between 4.5°C to 6.4°C below normal and “severe cold” when maximum temperature is 6.5°C below normal. The criteria are different for hills stations and coastal sites.

“A western disturbance (a storm originating in the Mediterranean region) that affected northwest India brought intense rainfall across northern states — as its byproduct, we’ve had moisture and fog along with clouds,” said Mrutyunjaya Mohapatra, the IMD’s director-general.

“These cloud conditions are preventing sunlight from penetrating and heating the ground, leading to fall in maximum temperatures,” Mohapatra told The Telegraph. But the fog and cold are also preventing a cold wave — marked by fall in minimum temperatures. A cold wave is typically preceded by clear skies.

The IMD has also predicted a wet spell in the western Himalayan region starting December 31 that is likely to bring rain, thundershowers or snow over Jammu and Kashmir, Himachal Pradesh and Uttarakhand up to January 2 and rain over central India and eastern India up to January 3.

States across northern India have experienced cold to severe cold days over the past 10 days under the influence of cold northwesterly winds.

The IMD said it observed the “most severity” on December 25 when the most number of weather stations recorded temperatures 7 to 12 degrees below normal.

The minimum temperatures on Friday were 3.1°C to 5°C below normal across northern and eastern India, including Delhi, Himachal Pradesh, eastern Uttar Pradesh, northern Bengal and Sikkim, and were 1.6°C to 3°C below normal in Bihar, Gangetic Bengal, and northern Madhya Pradesh.

Mohapatra said the IMD temperature records show that the average December temperature this year has been 19.5°C. It was 17°C in 1997.