Mercury dips, cold northwesterly winds improve air quality in Delhi

The mercury dipped but remained above normal in the Capital on Monday even as cold northwesterly winds improved the air quality to the moderate category and a shallow fog reduced visibility. The minimum temperature of 10.3°C was four degrees above normal. It was 13°C a day earlier. The India Meteorological Department (IMD) said the minimum was likely to dip by another 2-3°C in and hover around 7°C on Tuesday.

An average Air Quality Index of 179 (moderate) was recorded at 8am on Monday compared to 225 (poor) at 4pm on Sunday as northwesterly winds returned on Sunday due to a western disturbance that brought rain across the northwestern plains on Friday and Saturday.

“The impact of strong northwesterly winds is expected on December 31 and January 1 too. This, coupled with clear skies will help mercury dip further. Days will also remain fairly cold, with the maximum remaining below normal,” said private forecaster Skymet Weather’s vice president Mahesh Palawat. He added another western disturbance was expected to impact the region from January 2.

The shallow fog reduced visibility to 600 metres at Safdarjung, which is representative of Delhi’s weather, at 5:30am

On Sunday, the IMD forecast a return of cold wave conditions in isolated parts of northwest India and issued an alert for moderate to dense fog across National Capital Region in the early hours of the day until January 1.

“Although a cold wave is unlikely in Delhi, the minimum will still dip by around 5-6°C as cold northwesterly winds persist in the region following rain and fresh snowfall. Cold wave conditions are likely in isolated pockets of Punjab and Haryana-Chandigarh from December 31 until January 2,” an IMD official said.

The minimum temperature below 10°C or 4.5°C or more below normal is classified as a cold wave.