Yesterday, Delhi's temperature dropped below 20°C as fog kept the sun away for all but a brief window of a couple of hours in the afternoon, leaving people shivering in what was the coldest daytime temperature recorded this winter.

At 19.8°C, the maximum on Friday, December 29 was perceptibly colder than the 21°C recorded the previous day, even though the night-time temperature, or minimum, settled four notches above normal for this time of the year at 10.7°C.

While both these numbers were yet to meet thresholds for a coldwave or “cold day” temperatures, the India Meteorological Department (IMD) predicted the daytime chill to persist since a layer of fog in the higher altitudes that has been blocking the sun is not predicted to lift for another couple of days.

Low daytime temperatures can exacerbate people’s exposure to the cold and generally make the winter feel more intense since this is when people are usually outside of the comfort of their homes.

IMD said dense fog was recorded for three hours in the early hours, with visibility dropping to a low of 150 metres between 6 am and 9 am at Palam. This was the fifth consecutive dense fog day in Delhi.

The lowest visibility at Safdarjung – representative of Delhi’s weather – was recorded at 200m and rose to a maximum visibility of 800m during the day

The IMD classifies fog as “shallow” when visibility is between 500 and 1,000m; “moderate” when it is between 200 and 500m; “dense” when it is between 50 and 200m; and “very dense” when it is lower than 50 metres.

“Fog persisted through the day at Safdarjung and we also had fog at the upper-level of the atmosphere, with a layer of fog stretching from Punjab, all the way to the Indo-Gangetic Plains. This did not allow sunlight to penetrate through and subsequently kept the maximum temperature below normal in most places,” said Kuldeep Srivastava, scientist at IMD.

Low daytime temperatures can exacerbate people’s exposure to the cold and generally make the winter feel more intense since this is when people are usually outside of the comfort of their homes.