The India Meteorological Department said that "severe cold day (SCD) conditions were observed in most pockets over Punjab, Haryana, Chandigarh, Delhi, Uttar Pradesh and Bihar, and in isolated pockets over north Rajasthan, cold to severe cold day conditions in many pockets over Madhya Pradesh, in isolated pockets over West Bengal and cold day conditions in some pockets over Jharkhand & north Chhattisgarh."
As Delhi residents shivered in the cold, the IMD said that the city's mean maximum temperature in December has dipped below 20 degrees Celsius only four times in past 118 years - in 1919, 1929, and 1961 with the last in 1997.
The reason behind the cold wave is "due to persistence of cold northwesterly winds in lower levels over northwest India and other favourable meteorological conditions", said the Met department.
The IMD forecast: "Cold wave to severe cold wave conditions in some pockets over Haryana, Chandigarh, Delhi, north Rajasthan and Bihar and in isolated pockets over Punjab, Uttar Pradesh, Madhya Pradesh, Odisha and West Bengal and Sikkim during the next 2 days, in north Rajasthan and Uttar Pradesh during the next 3 days and over north Madhya Pradesh, Bihar Jharkhand, sub-Himalayan West Bengal & Sikkim and Odisha during the next 2 days and over northeastern India during next 4-5 days."
It has also predicted dense fog over Delhi which could affect visibility.
The Met department also predicted rainfall which could add the winter chill next week.
"Northwest and central India are very likely to experience fairly widespread to widespread rainfall accompanied with hailstorm at isolated places during December 31 and January 1 and 2 in eastern part of India."
At least 21 Delhi-bound trains were delayed from two to six hours due to dense fog, but flights operated normally from Delhi airport. "The runway visibility is good and flight operations are normal at #DelhiAirport," the airport said in a tweet.
Kargil district in Ladakh was the coldest place, recording a minimum temperature of minus 30.2 degrees Celsius.
( With inputs from IANS )