The national capital recorded a minimum temperature of 12.5 degrees Celsius on Thursday, the lowest in October in 26 years, according to the India Meteorological Department (IMD).
The normal minimum temperature for this time of the year is between 15 to 16 degrees Celsius, it said.
Kuldeep Srivastava, the head of the regional forecasting centre of IMD, said the last time Delhi recorded such a low temperature in October was in 1994.
The national capital had recorded a minimum of 12.3 degrees Celsius on October 31, 1994, according to IMD data.
The city recorded its all-time low temperature (9.4 degrees Celsius) on October 31, 1937, Mr Srivastava said.
The senior IMD scientist said the absence of cloud cover was the major reason for such low minimum temperatures this time.
Clouds trap some of the outgoing infrared radiation and radiate it back downward, warming the ground.
Another reason is calm winds which allow formation of mist and fog, Mr Srivastava said.
The minimum temperature is likely to dip to 11 degrees Celsius by November 1, the IMD added.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)