Cold wave continued unabated in the national capital on Friday, with the minimum temperature settling three notches below normal.
Twenty-one trains were delayed for a maximum of six hours in the north due to weather conditions.
"The minimum temperature was recorded at 4.2 degrees Celsius, three notches below normal," a meteorological department official said.
The humidity level was recorded at 86 per cent.
The maximum temperature will hover around 15 degrees Celsius, the official said.
The air quality was recorded in the "very poor" category (365), primarily due to low wind speed, high humidity and cold weather on Friday morning.
With a numbing cold continuing to sweep Delhi-NCR, the region is expected to record its second-coldest December since 1901, the weather department said.
According to the IMD, a "cold day" is when the maximum temperature is at least 4.5 notches below normal. A "severe cold day" is when the maximum temperature is at least 6.5 degrees Celsius below normal.