Delhi chilled to the bone as max mercury drops to 15.6°C

The national capital has been witnessing wintry mornings and nights since New Year’s Eve, making people shiver at homes and workplaces

The Capital recorded its coldest day of the season on Wednesday with a peak temperature of 15.6°C as icy winds and a band of heavy fog in the higher altitudes kept the city in the thick of winter.

Gurugram, India-January 03: Homeless people sit around a bonfire to warm themselves on a cold winter morning under a flyover at National Highway-48, Rajiv Chowk, in Gurugram, India, on Wednesday, 03 January 2024. (Photo by Parveen Kumar/Hindustan Times)

The maximum was 4°C lower than the average, and not 4.5 degrees – the threshold at which it qualifies for a “cold day” -- but an analysis of ambient temperatures taken every three hours since December 31 shows the city is colder than the peak highs suggest, and those figures are outlier recordings of when the sun briefly broke through the fog.

The peak temperature usually comes at a point somewhere in between 3pm and 4pm. The three-hour readings recorded by the India Meteorological Department (IMD), show the ambient temperature to be in the low double digits (10-11°C) for most parts of the day between 8.30am and 5.30pm, except for some hours between 2.30pm and 5.30pm.

“Cold day is a very strict classification which happens when the maximum, recorded at a particular time of the day, shows a departure of 4.5 to 6.4 degrees from the normal. However, when there is a fog persisting throughout the day, lack of sunlight causes cold day like conditions,” said Mahesh Palawat, vice president of Skymet.

Palawat added that a “constant shallow fog or haze in the upper layer” has blocked most of the sunlight from reaching the ground. “Except for two hours in the middle of the day, that is between 2pm and 4pm, there is very low amount of sunlight reaching past this upper haze which is why temperature drops so quickly after 4pm,” said Palawat.

Three-hour readings from Safdarjung illustrate how the rest of the day except for the brief afternoon window: the temperature was 9.6°C at 8.30am, 11.2°C at 11.30am, and 15.2°C at 2.30pm before it began to drop again, plummeting to 13.8°C at 5.30.

The maximum recorded at the station was 15.6°C. The station recorded a low of 7.3°C in the early hours.

How the weather is classified has implications for public health safety messaging. Typically, IMD issues a yellow or red alert if bad weather (cold wave, or extreme rain) is expected. No alert was issued for Wednesday. A yellow alert was issued for both Monday and Tuesday, forecasting possible cold day conditions.

Cold day conditions pose a unique risk since they pertain to the days being cold, instead of only the night or early hours. People are usually outside of the comfort of their homes in the daytime.

Multiple weather stations in Delhi recorded cold day conditions. Lodhi Road recorded a maximum of 14.6°C, Ridge recorded a maximum of 13.6°C while CDO Ghaziabad, Noida and SPS Mayur Vihar recorded a maximum of 11.5°C, 12.5°C and 12.3°C respectively. The minimum at all the stations remained below 10°C.

Health experts said prolonged exposure to such cold can be physically stressful for some people. “The blood vessels tend to shrink when it is biting cold, making it difficult for blood to flow smoothly. People may face breathing difficulty and those who already suffer from any heart ailments run a higher risk,” said Dr Upendra Kaul, chairperson, cardiology, Batra Hospital & Medical Research Centre.

IMD has forecast a gradual increase in temperature over the next few days. “Several weather stations in Delhi are likely to experience cold day conditions tomorrow but after that, the maximum should start going up,” said Kuldeep Srivastava, scientist at the IMD.

Srivastava added, “Upper-level fog is still persisting and will continue to persist on Thursday. Moreover, moderate surface level fog is expected to be seen tomorrow.”

Delhi’s air quality, meanwhile, remained in the “very poor” category, two days after the Commission for Air Quality Management (CAQM) in NCR lifted stage-3 or “severe” category measures under the Graded Response Action Plan (Grap).

Delhi’s average AQI was recorded at 341 (very poor) as per Central Pollution Control Board’s national bulletin at 4pm. It was 340 (very poor) at 4pm on Monday and 346 (very poor) on Sunday. Forecasts by the Early Warning System (EWS) for Delhi – a forecasting model under the ministry of earth sciences -- said Delhi’s air quality should remain “very poor” till January 6 now.