In the plains, the IMD declares a cold waveif the minimum temperaturedips to 4 degrees Celsius. A severe cold wave is when the minimum is 2 degrees Celsius or less.
The India Meteorological Department said the mercury may drop further by New Year's Eve.
Cold wave conditions are predicted in parts of the city over the next three days, it said.
Kuldeep Srivastava, the head of the regional forecasting centre of the IMD, said a Western Disturbance ledto "scattered to fairly widespread" snowfall in Jammu and Kashmir, Ladakh, Himachal Pradesh and Uttarakhand.
Cold and dry northerly/northwesterly winds from the western Himalayas have been barreling through the plains, bringing theminimum temperature in north India down, he said.
According to IMD, a coldwaveis also declared when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches less than normal.
A "severe" cold wave is when the minimum temperature dips to two degrees Celsius or the departure is more than 6.4 degrees Celsius.
On December 20, the Safdarjung Observatory recorded a minimum of 3.4 degrees Celsius, the lowest this season so far.
Delhi'sairqualitywas recorded in the "poor" category on Tuesday morning.
The city's24-hour average airqualityindex was 265 on Tuesday,253 on Monday, 396 on Sunday,337 on Saturday, 357 on Friday, 423 on Thursday and 433 on Wednesday.
An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".
Officials at the India Meteorological Department (IMD) said favourable wind speed, up to 15 kmph, aided in the dispersion of pollutants.
(Only the headline and picture of this report may have been reworked by the Business Standard staff; the rest of the content is auto-generated from a syndicated feed.)
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