A punishing cold wave swept Delhi on Monday with the minimum temperature at the Safdarjung observatory, the city's base station, plunging to 1.4 degrees Celsius, the lowest in the month since January 1, 2021.
The India Meteorological Department (IMD) said the mercury may dip to 1 degree Celsius on Tuesday. If that happens, it would be the lowest minimum temperature in at least 15 years in the city.
Safdarjung had recorded a minimum temperature of 1.1 degree Celsius on January 1, 2021. It logged a minimum of 1.9 degrees Celsius on January 8 this year.
The all-time low of minus 0.6 degree Celsius was recorded on January 16, 1935.
The minimum temperature in the national capital has dropped by around nine notches in just two days. It was 10.2 degrees Celsius on Saturday and 4.7 degrees Celsius on Sunday.
The weather station at Lodhi Road, where the IMD headquarter is located, recorded a minimum temperature of 1.6 degrees Celsius Monday morning.
The minimum temperature plunged to 2.8 degrees Celsius at Ayanagar in southwest Delhi, two degrees Celsius at the Ridge in central Delhi and 2.2 degrees Celsius at Jafarpur in west Delhi.
Delhi saw an intense cold wave spell from January 5 to 9, the second longest in the month in a decade, according to IMD data.
It has also recorded over 50 hours of dense fog this month so far, which is the highest since 2019.
A senior IMD official said Delhi will get excellent sunshine in view of clear skies and the absence of fog and day temperatures will be normal.
"Cold wave conditions will prevail during the night and early morning. So, this cold spell cannot be compared with the previous one," he said.
Mahesh Palawat, a senior meteorologist at Skymet Weather, said there has been heavy snowfall in the Himalayan region due to a strong western disturbance (WD) and cold northwesterly winds started sweeping the plains after the WD retreated on January 14.
"The sharp dip in the temperature is due to clear skies which allowed the infrared radiation (heat from the sun) to escape back into space at night," he said.
The IMD had earlier issued an orange warning for a cold wave in Delhi till January 17-18.
The MeT office on Monday said cold wave conditions will abate from January 19 under the influence of two western disturbances which are likely to affect the region in quick succession.
When a western disturbance -- a weather system characterised by warm moist winds from the Middle East -- approaches a region, the wind direction changes. The chilly northwesterly winds from the mountains stop blowing, leading to an increase in temperatures.
In the plains, a cold wave is declared if the minimum temperature dips to 4 degrees Celsius or when it is 10 degrees Celsius and 4.5 notches below normal.
A severe cold wave is when the minimum temperature dips to 2 degrees Celsius or the departure from the normal limits is by more than 6.4 notches.