The month of October was the coldest in 58 years in the national capital, according to India Meteorological Department (IMD) data.
The mean minimum temperature in October this year was 17.2 degrees Celsius, the lowest since 1962, when it was 16.9 degrees Celsius, the IMD said.
Normally, Delhi records a mean minimum temperature of 19.1 degrees Celsius in October.
On Thursday, Delhi recorded a minimum temperature of 12.5 degrees Celsius - the lowest in the month of October in 26 years. The last time Delhi recorded such a low temperature was in 1994.
The national capital had recorded a low of 12.3 degrees Celsius on October 31, 1994, according to the IMD data.
The normal minimum temperature for this time of the year is 15-16 degrees Celsius, the IMD said.
Kuldeep Srivastava, the head of the IMD's regional forecasting center, said the absence of cloud cover is a 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.
Delhi had recorded its all-time low temperature of 9.4 degrees Celsius on October 31, 1937, he said.
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