Trains and flights were hit for the second day in a row as a thick fog cover descended on the national capital region on Tuesday with visibility dropping to 300 metres.

At least 24 flights were delayed and over six cancelled. While 21 trains were cancelled and 64 delayed besides 24 rescheduled due to heavy fog in several parts of northern India.

The minimum temperature was recorded at 8.4 degrees Celsius, a notch above the season's average. The maximum was likely to hover around 21 degrees.

The sky will remain clear during the day, an India Meteorological Department official said.

Operations at the Indira Gandhi International (IGI) Airport here were severely affected due to low visibility. Flights were stopped from taking off between 11 p.m. and 12 a.m. as visibility was nil.

Landing of almost all flights were delayed, an airport official said. The visibility later improved to 100 metres at 3 a.m. and to 200 metres at 6 a.m.

At 8.30 a.m., humidity was 97 per cent and visibility improved to 300 metres.

Monday's maximum temperature settled at 20.1 degrees Celsius, one notch above the season's average while the minimum was recorded at 5.7 degrees Celsius, a notch below the season's average.