Fog started accumulating in the wee hours and became thick around 6 am, the Met department said.
While general visibility was reduced to zero, runway visibility fell to less than 50 metres, disrupting the schedules of around 50 domestic and international flights at the Indira Gandhi International airport here. The city is likely to experience dense fog tomorrow also, the Met office said.
The railways cancelled the Bhopal Shatabdi Express leaving New Delhi station at 6.15 this morning because of dense fog and rescheduled four trains.
The minimum temperature was recorded at 6.8 degree Celsius today against yesterday's minimum of 5.6 deg C. Yesterday's maximum was recorded at 18.1 deg C, giving some respite to the people from intense cold.