India, Jan. 7 -- 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.

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.

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