"The heavy backlog of trains led to many delays owing to fog in Delhi and other northern regions," a Northern Railways spokesperson said.
The fog also disrupted operations at Indira Gandhi International airport, delaying some flights.
"Ten flights were delayed -- seven international and three domestic. Three domestic flights and an international flights were also cancelled," said a Delhi International Airport Limited official.
Visibility in the city at 8.30am was reduced to 500 metres, an India Meteorological Department (IMD) official said.
Many wrapped themselves in layers of woollens to combat the icy winds. Homeless basked themselves in the mild sun, bracing up for a bone-chilling evening.
"There was dense fog cover in the morning. It was tough steering the car as nothing was visible," said Vineet Malhotra of Patparganj area in east Delhi.
Tuesday's maximum temperature was a notch below average at 20.4 degrees while the minimum was three notches below average at 4.8 degrees.