Delhi logs coldest night this season; min at 3.9°C

The dense fog cleared by 11am and sharp sunlight covered most of the city. The maximum peaked at 19.3°C

Delhi recorded its coldest night of the season on Friday with the minimum temperature dipping to 3.9 degrees Celsius (°C) — three degrees below normal — making for a frosty morning, even as dense surface-level fog significantly dropped visibility to zero at the Indira Gandhi International (IGI) airport for over four hours, the India Meteorological Department said.

A cold and foggy winter morning near Akshardham temple. (Sanjeev Verma/HT Photo)

However, the dense fog cleared by 11am and sharp sunlight covered most of the city. The maximum peaked at 19.3°C — a degree below normal — making for the warmest daytime temperature this month. It was 20.3°C on December 30.

The previous lowest minimum so far this winter was 4.9°C on December 15 and it did not go below 5°C on any other day.

Very dense surface-level fog also returned to the Capital, impeding transit operations at the airport for over four hours — from 4.30am to 9.30am — and delaying at least 100 delays within that period. Similar delays were reported in the case of trains as well and the Northern Railways said that at least 39 trains were delayed by an hour.

The Capital, this season, has recorded three “cold days” when the maximum was 4.5°C or more below normal. However, no “cold wave” has officially been recorded this winter so far, as the classification can only be made in the plains when the minimum reading is below 4°C for two consecutive days. To be sure, the city recorded isolated “cold wave” conditions in areas like Lodhi Road at 3.6°C on Friday.

The low minimum also translated into the city recording its highest-ever peak power demand for the winter months which was clocked at 52,701MW at 10.49 am on Friday. The previous highest ever for Delhi’s winter months was 5,611 MW on January 10, 2024, and 5,559 MW on January 5, 2024. Delhi’s power distribution companies said they were able to meet this demand successfully.

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

The dip in minimum temperature over the last three days has been down to the upper-level fog gradually dissipating from parts of northwest, central and east India, which has brought clear skies after nearly two weeks. When upper-level fog or cloudiness prevails over a region, the maximum temperature remains low as sunlight does not penetrate to reach the surface. In such a situation, the minimum is usually higher than normal as heat remains trapped even at night.

A clear sky has the opposite effect, making days warm as ample sunlight reaches the surface. The same heat is lost at night in the absence of dense fog.

“The dense fog at surface level returned due to the clear skies aided by low wind speed,” said Kuldeep Srivastava, scientist at IMD.

IMD forecasts the minimum to rise by a degree on Saturday, owing to an approaching western disturbance. It may fall once again on Sunday, as clear skies are expected on that day. Meanwhile, the maximum is forecast to remain high — hovering around 19°C-20°C over the next two days. The lowest maximum recorded this season was 12.5°C on January 4.

“A feeble western disturbance is being recorded across the northern plains, which may lead to some cloudiness on Saturday. We expect a maximum of around 5°C on Saturday. With clear skies on Sunday, the minimum may again drop to around 4°C,” he said.

Delhi’s air remained “very poor” and the average air quality index clocked a reading of 340 (very poor) at 4pm on Friday. It was 348 (very poor) at the same time on Thursday. Forecasts by the Early Warning System (EWS) for Delhi show Delhi’s AQI will likely remain “very poor” now for the next few days.

“Delhi’s air quality is likely to be in the ‘very poor’ category from January 13 till 15. The outlook for the subsequent six days shows the air quality is likely to remain in the ‘very poor’ category,” said EWS in its daily bulletin on Friday.