Delhi's mean maximum temperature for December stood at 18.76 degrees (Representational)

Reeling under a prolonged cold spell, the national capital has recorded the coldest December since 1901, officials said on Tuesday.

Delhi's mean maximum temperature (MMT) for December stood at 18.76 degrees Celsius, the second-lowest after 17.3 degrees Celsius recorded in December 1997.

"Only four times the mean maximum temperature for December has remained equal to or less than 20 degrees Celsius -- 1919, 1929, 1961 and 1997," an official of the India Meteorological Department (IMD) said.

The MMT for the month was 19.8 degrees Celsius in 1919 and 1929, while it was 20 degrees Celsius in 1962, the official said.

Head of IMD's regional weather forecasting centre Kuldeep Srivastava, said the city witnessed another "cold day" on Tuesday.

With this, December has recorded 18 consecutive "cold days" or an 18-day "cold spell", the maximum after 17 cold days in December 1997.

After 1992, Delhi has had cold spells only in four years - 1997, 1998, 2003 and 2014.

According to the IMD, a "cold day" is when the maximum temperature is at least 4.5 notches below normal.

A "severe cold day" is when the maximum temperature is at least 6.5 degrees Celsius below normal.

The prolonged cold wave and absence of adequate sunshine due to a very dense fog caused the mercury to plummet drastically, making Monday the coldest day (with a maximum of 9.4 degrees Celsius) since 1901.