As the Delhi-NCR experiences bone-chilling temperatures and thick fog, the India Meteorological Department (IMD) explained on Wednesday the reason why a yellow alert for a cold wave has been issued for several cities across northern India, including the national capital.

The IMD has issued a yellow alert until Thursday, predicting dense to very dense fog and chances of “cold day” conditions, as a combination of upper-level fog and icy-cold northwesterlies left the city shivering on Tuesday, HT earlier reported.
Why is a cold warning in place across parts of northern India?
There is a complete layer, referred to as a clear clouds dense fog layer, which prevents sunlight from reaching the earth directly, news agency PTI quoted IMD scientist Naresh Kumar as saying on Wednesday.
This is the reason why temperatures recorded during the daytime are lower than usual, making way for the weather department to put a cold wave in place for the next few days over several north Indian states.
“Specifically, if we talk about Punjab, Haryana, Uttar Pradesh, and even Bihar, we have issued cold day warnings for the next two to three days,” Kumar said.
{{/usCountry}}“Specifically, if we talk about Punjab, Haryana, Uttar Pradesh, and even Bihar, we have issued cold day warnings for the next two to three days,” Kumar said.
{{/usCountry}}Apart from the lower temperatures recorded during the day, temperatures recorder over the early morning hours hovered around 4 degrees Celsius or even lower in states including Punjab and Haryana. These are the reasons why IMD issued a cold wave warning, Kumar explained.
Coldest day in Delhi
IMD had said that parts of Delhi recorded ‘cold day’ conditions on Tuesday with possible chances of temperatures dropping further until January 15, Hindustan Times reported earlier.
According to IMD data from Safdarjung station, the national capital logged a maximum temperature of 15.7 degrees Celsius and a minimum of 8.6 degrees Celsius on Wednesday.
‘Very poor’ AQI in the capital
According to data from central pollution control board (CPCB)'s Sameer app, air quality in the national capital hovered in the ‘very poor’ category on Wednesday as the air quality index (AQI) shot up as high as 336.
Nehru Nagar recorded the worst air quality among all stations in Delhi with a score of 360 on the AQI scale.
Delhi had breathed ‘poor’ air quality on Tuesday.
IMD on Wednesday issued a yellow alert for dense fog as it expected poor visibility over the morning and forenoon hours.