Temperatures fell to a minimum for the day of 4.8C while the maximum temperature in the city was down 11 degrees at 9.8C.
The Meteorological Office said it was the first time since records began in 1969 that the city’s maximum was in single digits.
Forecasters say the unusual conditions will continue for the next few days.
Unlike the West, Indian homes rarely have central heating.
The dense fog has also been causing travel chaos, with air and rail traffic severely disrupted.
More than 30 flights were either cancelled or diverted on Wednesday while the previous day more than 100 flights were affected as visibility fell to near-zero levels, officials said.
Dozens of trains were also cancelled or delayed due to the poor weather.
The cold snap has also been sweeping through many parts of the northern states of Uttar Pradesh, Rajasthan, Punjab, Haryana, Himachal Pradesh and Jammu and Kashmir.