Eighteen flights were cancelled because of poor visibility, said Kapil Sabarwal, spokesperson for the Indira Gandhi International Airport.
According to a statement issued by the airport, visibility was less than 50 meters Wednesday morning.
"Three trains were cancelled and 39 rescheduled due to poor visibility," said spokesman A.S. Negi of Northern Railway.
There were clearer skies by afternoon.
The day's maximum temperature was 23 degree Celsius, normal for this time of the year.
The minimum temperature was one notch above the season's average, at 8.9 degrees Celsius.
India Meteorological Department (IMD) has said Thursday will see heavy fog in the morning and evening.
"The afternoon will see sunny skies, and the maximum and minimum temperature will hover around 22 and 10 degrees Celsius," an IMD official said.
Foggy conditions will continue in Delhi for a few days, he said.
Temperatures Tuesday were in the same range, with the maximum and minimum at 22.6 degrees and 9 degrees Celsius.
--IANS (Posted on 18-12-2013)