Delhi shivering at night, but yet to register a ‘cold wave’
Delhi recorded a minimum of 5.8°C and a maximum of 18.1°C as sunlight helped lift daytime temperatures
The Capital has not recorded a “cold wave” this winter — a condition when the minimum temperature falls to 4.5 degrees Celsius (°C) or more below normal — the India Meteorological Department (IMD) said on Thursday, attributing this to the dense layer of upper-level fog prevailing over the northern plains over two weeks.
Delhi recorded a minimum of 5.8°C and a maximum of 18.1°C as sunlight helped lift daytime temperatures slightly, but clearing skies also meant colder nights.
The minimum temperature has not dropped below 5°C so far in January and the season’s lowest of 4.9°C — the only time it dipped below 5°C this winter — was on December 15.
Delhi has, however, recorded three “cold days” this season, when the maximum has been 4.5°C or more below normal, leading to daytime chills. According to weather officials, the dense fog has impeded sunlight from breaking through on most days, which has capped the maximum to under 20°C this year till Thursday.
At night, the dense fog prevents whatever heat has reached the surface during the day from escaping, subsequently keeping the nighttime temperatures from being too frigid, said Kuldeep Srivastava, scientist at IMD, adding that with the fog finally clearing across the northern plains on Thursday, nighttime lows are likely to dip on Friday.
In previous years, the minimum in the corresponding period till January 11 has reached as low as 1.1°C — a number of seasonal lows were, coincidentally, recorded on January 1. The minimum was 1.9°C in 2023 (January 8), 4.2°C in 2022 (January 1), 1.1°C in 2021 (January 1), 2.4°C in 2020 (January 1) and 4°C n 2019 (January 1). On January 1 this year, the minimum in Delhi was 10.1°C.
IMD forecasts that the minimum may touch 5°C on Friday before a western disturbance brings cloudiness to the region and raises it to 8-9°C again.
On Wednesday, Delhi’s minimum was 7.1°C, preceded by 7.8°C on Tuesday.
“The minimum could be between 4.5°C to 5.5°C at Safdarjung — Delhi’s base weather station — as there will be limited fog and cloudiness to trap the heat. We will then see two successive western disturbances, which will bring the cloudiness back, making for a night-time temperature around 8-9°C till January 17,” Srivastava added.
Thursday was generally sunny and windy, and the maximum temperature rose to 18.1°C — two degrees below normal. It was 15.2°C a day earlier.
IMD officials said that January has been comparable to 2022 when a similar dense fog made for high minimum temperatures. “Even then, the minimum dipped lower than it has been this January,” Srivastava said.
December ended with an average monthly minimum of 8.5°C. This was 0.1°C higher than the monthly long-period average, but the highest average minimum for December in six years, since 2017, when it was 9.1°C.
The average minimum temperature so far in January has been 7.8°C, almost a degree higher than the long-period average of 6.9°C for the first 11 days of the month.
Forecasts for Friday said there will be ample sunshine during the day, and the maximum may be around 19°C and the minimum around 5°C. On Saturday, the maximum will remain around 19°C and the minimum might rise to 8°C.
Delhi recorded shallow fog on Thursday while dense fog was recorded for an hour — between 4am and 5am — when visibility was 100 metres at Palam. This led to a handful of flight delays at the Indira Gandhi International (IGI) airport. Northern Railway reported that 24 trains were delayed by around an hour in the early hours.
Mahesh Palawat, vice president at the private forecaster Skymet, said the absence of sunlight and clear skies was the key reason behind warm nights over the last two weeks. “We generally see the lowest minimum of the season in the first two weeks of January. We have seen a lot of dense fog across the northern plains, which has kept the minimum in check and the maximum falling. The second half of January is always comparatively warmer and the minimum should rise even further after January 15,” he said, adding that other parts of northwest India recorded similar conditions this season.
Delhi’s 24-hour average air quality index (AQI) deteriorated to 348 (very poor) at 4pm on Thursday, based on the Central Pollution Control Board’s bulletin. It was 273 (poor) a day earlier. Delhi’s air had improved to “poor” after 20 days.
Forecasts by the Early Warning System (EWS) for Delhi — a forecasting model under the ministry of earth sciences — show the AQI will likely remain “very poor” for the next few days. “Delhi’s air quality is likely to be in the ‘very poor’ category from January 12 till 14. 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.