Delhi and many other parts of North India continued to reel under a cold spell on Thursday, with a forecast of cold or severe cold day conditions for the next five days in many states, the Hindustan Times reported.

On Wednesday, Delhi had recorded a maximum temperature of 12.7 degrees Celsius, nine degrees below normal. The minimum temperature was 5.4 degrees Celsius. On Thursday morning, the India Meteorological Department reported the minimum temperature in the national Capital also at 5.4 degrees Celsius, three degrees below normal.

Delhi is witnessing the longest cold spell in December in 22 years. Since 1993, Delhi has had a cold spell only in four years – 1997, 1998, 2003, and 2014. Most weather stations in Delhi, except Safdarjung, have recorded a cold spell for 12 days in a row by Thursday. The cold spell is expected to continue till Friday.

According to the weather department, a “severe cold day” is registered when the minimum temperature drops to less than 10 degrees Celsius and the maximum temperature is at least 6.4 degrees Celsius below normal. On the other hand, a “cold day” is registered when the minimum temperature is less than 10 degrees Celsius and the maximum is 4.4 degrees Celsius below normal.

The cold snap has affected parts of Haryana, Punjab and Uttar Pradesh as well. Narnaul in Haryana recorded a minimum temperature of 3.2 degrees Celsius on Wednesday – two notches below normal. On Thursday, it recorded a minimum temperature of 2.5 degrees Celsius, three degrees below normal.

On Wednesday, Hisar recorded below normal minimum temperature at 4.1 degree Celsius. The minimum temperature recorded in the town on Thursday was four degrees Celsius.

Faridkot in Punjab was the coldest in the state on Wednesday with a minimum temperature of 4.6 degree Celsius. On Thursday, it recorded a minimum temperature of 3 degrees Celsius.

The IMD has said that cold wave conditions are likely to set in over Delhi from December 28 to December 30. There is a possibility of rain or thunderstorms on December 31 and January 1, it added. Minimum temperatures may rise marginally later.

Meteorologists have said that the unusually cold conditions are due to a western disturbance. The disturbance leaves much moisture in the atmosphere, leading to dense fog. “After sunrise when the surface warms a little the fog layer lifts up but not enough,” Kuldeep Srivastava, head of the IMD’s regional Weather Forecasting Centre, told the Hindustan Times. “It continues to hang close to the surface in the form of a low cloud cover. This is the main reason sun is not able to warm the surface and day temperature is low.”

K Sathi Devi, head of National Weather Forecasting Centre, said that when the western disturbance moves away, cold air moves in from the higher reaches of northwestern India. “There are usually clear skies and very cold nights, the combination of these conditions brings on a cold wave,” she added.