"Delhi so far has recorded longest and extremely cold day spell in December month, since 1997," the India Meteorological Department said.
It also said that while Delhi had witnessed 17 cold days in December 1997, this time it has recorded 10 cold days in a row. Before this, in December 2014, Delhi saw severe cold continuing for eight consecutive days, the IMD added.
The India Meteorological Department said Wednesday will remain cold and the conditions will further deteriorate to "severe cold" later in the day.
The maximum temperature for Wednesday was likely to hover around 15 degree Celsius, the IMD said.
On Tuesday, the maximum temperature was recorded at 15 degree Celsius, six notches below the season's average, while the minimum was 5.5 degrees C, three notches below the season's average.
Not just Delhi, but neighbouring Noida, Ghaziabad, Faridabad and Gurugram were also under the grip of severe cold wave.
The weather office said the cold day to severe cold day conditions will continue in the city till December 28, along with dense to very dense fog in night and morning hours.
The air quality of the national capital was recorded under 'very poor' category. According to the Centre-run System of Air Quality and Weather Forecasting (SAFAR), the overall air quality index (AQI) of Delhi was recorded at 369 on Wednesday morning.
SAFAR suggests a slight improvement in wind speed and ventilation, and a marginal improvement in AQI is forecast for Thursday but within the very poor category.
"From Friday onwards winds are forecast to slow down for three days. On Friday the AQI is forecast to deteriorate towards the higher end of the very poor category. The dense fog in the morning hours is likely to continue for the next two days under favourable meteorological conditions," the SAFAR said.
It also predicts that low surface wind speed and low ventilation are forecast for an extended period from Friday and likely to lead to the accumulation of pollutants. By December 29, the AQI is likely to touch higher levels, it said.
( With inputs from IANS )