Cold-day conditions prevailed in parts of north India on Friday though the maximum temperatures rose slightly amid clear skies and sunshine during the day.
The India Meteorological Department (IMD) said 'cold' to 'severe cold day' conditions continued at many places over Punjab, Haryana, Uttar Pradesh, Uttarakhand and Rajasthan.
The maximum temperatures remained in the range of 10-20 degrees Celsius, with Amritsar in Punjab clocking 9.4 degrees Celsius, around nine notches below normal.
A cold day is when the minimum temperature is less than or equal to 10 degrees Celsius below normal and the maximum temperature is at least 4.5 degrees Celsius below normal. A severe cold day is when the maximum is 6.5 degrees Celsius or more below normal.
A cold wave swept through Delhi with the city's primary weather station, Safdarjung observatory, recording a minimum temperature of 3.9 degrees Celsius, the lowest so far this season. The capital logged a maximum temperature of 19.3 degrees Celsius.
Ambala in Haryana recorded 11 degrees Celsius, which was seven notches below normal, while Ludhiana and Patiala in Punjab clocked 11.4 degrees Celsius and 12.1 degrees Celsius respectively, around six notches below normal.
Ganganagar in Rajasthan shivered at 12.7 degrees Celsius, which was seven notches below normal for the season.
Bareilly in Uttar Pradesh recorded a maximum temperature of 12.7 degrees Celsius, around six notches below normal.
Cold day to severe cold-day conditions have been prevailing over many parts of north India since December 30-31.
In the morning, a layer of fog draped over the Indo-Gangetic plains and extended up to the northeast, bringing down visibility and affecting rail movement.
A spokesperson for the Indian Railways said the fog impacted the schedule of '23 trains arriving in Delhi'.
Satellite imagery showed a layer of fog or low-level clouds over Punjab, Haryana, Delhi, Uttar Pradesh and Bihar, extending up to northeast India.
Patches of fog were also visible over Odisha.
The IMD said visibility levels dropped to zero at Delhi's Palam observatory, near the Indira Gandhi International airport.
One could see up to a distance of 200 metres at the Safdarjung airport, an IMD official said.
Visibility levels plummeted to 25 metres in Amritsar in Punjab and Lucknow and Varanasi in Uttar Pradesh, 50 metres in Chandigarh, Bareilly, Bihar's Purnia and Assam's Tezpur, and 200 metres in Ambala and Ganganagar.
According to the IMD, very dense fog is when visibility is between zero and 50 metres, between 51 and 200 metres is dense, between 201 and 500 metres moderate, and between 501 and 1,000 metres shallow.
The IMD said dense to very dense fog is likely during the morning hours in parts of northwest India over the next three to four days.
