With most weather stations, other than Safdarjung, recording on Tuesday, maximum temperatures at least 4.5 degrees Celsius lower than the normal maximum temperature. Delhi is facing its longest cold spell in 22 years.
Thus far, Delhi’s cold spell this December has been eight days if only Safdarjung station is considered and eleven days if other stations are considered. In 1997, there was a cold spell for 13 days in December. “Delhi so far has recorded longest and extreme cold day spell in December month, since 1997,” the India Meteorological Department (IMD) said on Tuesday.
Since 1993, Delhi has seen cold days only in 10 years, and had a cold spell only in four (before this year) — 1997, 1998, 2003, and 2014.
The IMD statement added that a cold spell has prevailed over north Rajasthan and Uttar Pradesh during the same period from December 15 to 24; in parts of Bihar between December 17 and 22 and over northern parts of Madhya Pradesh between December 17 and 20.
Delhi recorded a cold day on Tuesday also with all stations in Delhi except Safdarjung station meeting the criteria (a maximum temperature 4.5 degrees C below normal). The maximum temperature at Safdarjung was 17.2 degrees, 4.2 degrees below normal while the minimum temperature was 5.7 degrees C, 2 degrees below normal.
The reason cold spells are uncommon is because they got boosted up by multiple factors, all acting together.
The main difference between a cold spell and a cold wave is that the former involves lower-than-normal maximum or day temperatures for two-three days in a row while the latter involves lower-than-expected minimum or night temperatures for at least more than one day. In the coming days we could see both, experts say.
IMD on Tuesday said: “due to favourable meteorological conditions, dense to very dense fog in the morning hours and cold day to severe cold day conditions is very likely over Delhi in the next two days.”
Dense to very dense fog in the morning hours and cold day conditions are also likely over Uttar Pradesh during the next five days.
The wind speed on Tuesday was also very low at only 6 to 8 kmph in Delhi making conditions unfavourable for dispersion. The AQI reading was 383 — in the very poor category, almost bordering severe.