Rail and air services continued to remain disrupted on Friday as thick fog engulfed the national capital, bringing visibility down to 100 metres. Over 100 flights were affected.
According to the India Meteorological Department (IMD), visibility is likely to improve during the day.
The weatherman said the dense fog was due to a large amount of moisture in the air.
"Rain received in the national capital last week has left moisture in the air, which is responsible for the fog," said an IMD official.
The national capital recorded a minimum of 7.4 degrees Celsius, a notch below average for this time of the season.
Fog disrupted air and train schedules -- over 100 international and domestic flights and over 70 trains were affected.
"Runway visibility dropped below 50 metres early Friday and the CAT III landing system was activated to facilitate flight operations," an airport official said.
Northern Railways has set up a 24-hour helpline for passengers to check the status of trains. The helpline numbers for the New Delhi Railway Station are 23342954 and 23341074 ; for Old Delhi Railway Station 23967332 and 23962389 and for Hazrat Nizamuddin Railway Station 24355964 and 24359748.