A cold wave occurs in the plains when the minimum temperature is 10 degrees Celsius or below and/or is 4.5 notches lower than the season's normal for two consecutive days.
There is fog and low visibility across the Indo- Gangetic plains and northeast India, stretching from Punjab to Meghalaya, according to India Meteorological Department (IMD).
Dense to very dense fog was observed over Punjab, west Uttar Pradesh and moderate to dense fog was observed over Haryana, Chandigarh, Delhi, east Uttar Pradesh, Bihar, Assam and Meghalaya at 5.30 am on Sunday.
Visibility at Patiala and Bareilly was 25 metres each; 50 meters at Chandigarh, Bahraich, Gaya, Tezpur, Agartala and Dibrugarh and 200 m each at Amritsar, Ambala, Delhi-Safdarjung and Palam, Lucknow and Guwahati.
Cold day to severe cold day conditions occurred at a few places over Punjab and at isolated places over Haryana and east Uttar Pradesh on Saturday. Cold wave conditions occurred at isolated places over Punjab and Uttar Pradesh. The lowest minimum temperature over plains of northwest India on Saturday was 2.6°C, recorded at Churk in Uttar Pradesh.
On Sunday also, cold day to severe cold day condition is likely over parts of Punjab, Chandigarh and Uttar Pradesh.
According to IMD, a cold day or a severe cold day is classified as such based on two parameters—a minimum temperature of under 10 degrees C and maximum temperature of 4.5 degree C or 6.4 degree C below normal, respectively.
A cold wave occurs in the plains when the minimum temperature is 10 degrees Celsius or below and/or is 4.5 notches lower than the season's normal for two consecutive days. A cold wave is also declared when the minimum temperature is less than 4 degree C in the plains.