Delhi’s wintry nights... after grey, chilly days

The last time the minimum was lower than Monday’s figure was on December 15 (4.9°C), but days were sunny then with a peak of 25.4°C

The Capital woke up to its coldest morning in over three weeks on Monday with temperatures dropping overnight to a low of 5.3°C, before foggy conditions made for yet another grey, chilly day with the daytime peak reaching no higher than 17.5°C.

The minimum temperature on Monday dropped to 5.3°C, down from 8.2°C the day before. (Sunil Ghosh/HT Photo)

The temperatures recorded on Monday came a day after what promised to be a respite from bitterly cold conditions — the maximum oscillated between 12.5°C- 15°C for four consecutive days last week, the daytime peak feeling little different from the nighttime lows, even though the latter was higher than usual.

While those conditions were concerning for their own reasons -- people are usually more exposed to the cold during the day when they are outdoors -- the conditions on Monday pose a threat to those exposed to the cold at night, such as the homeless.

The last time the minimum was lower than Monday’s figure was on December 15 (4.9°C), but days were sunny then with a peak of 25.4°C.

“Clear skies on Sunday led to the decline in minimum temperature,” said Kuldeep Srivastava, scientist at India Meteorological Department (IMD).

“When there is no fog or cloud and skies are clear, more heat escapes once the sun has set and the minimum goes down. Similarly, more sunlight reaches the Earth’s surface, leading to a higher maximum, he said.”

But the latter was not to be throughout Monday as a blanket of fog returned. “There was a moderate upper-level fog observed today, due to which the maximum went down again. The maximum, however, should stay below 20 degrees throughout the week,” said the IMD official.

While no flights were impacted at Delhi’s Indira Gandhi International (IGI) airport, at least 20 trains – to and from Delhi -- were delayed by more than one hour on Monday morning, Northern Railway said.

The city was predicted to receive some spells of rain on Monday or Tuesday owing to the effects of an approaching western disturbance, which weather experts said on Sunday would lead to brief relief from the cold conditions --- western disturbance replaces the icy cold winds that blow in from the mountains this time of the year --- before temperatures plummet again towards the end of the week.

“The approaching western disturbances might cause light rain or drizzle in some isolated pockets of Delhi on Tuesday, even though the chances are even lesser than 50 percent. Cloudy skies will be observed throughout the day and shallow fog will persist in the early hours of the day,” Srivastava said.

IMD officials said no weather station in Delhi experienced “cold day” conditions on Monday, a classification that is applied when the maximum is 4.5 notches below normal and the minimum below 10°C. Monday’s maximum was one degree below normal, and the minimum two degrees below normal.

Some stations met this threshold — Mungeshpur recorded a maximum of 11.9°C and Jafarpur 12°C — but IMD officials said both were new automatic weather stations and did not have a defined ‘normal’, therefore, were not categorised as locations that recorded a cold day.

“It is anticipated that the minimum temperature in parts of Delhi-NCR will see an increase in the coming days due to the prevailing and approaching western disturbance. There are chances of rainfall as well but even if there is no rainfall, the minimum temperature is likely to increase in the region”, said vice-president, climate and meteorology at Skymet Weather, Mahesh Palawat.

Delhi’s air quality, meanwhile remained in the ‘very poor’ category, with a 24-hour average air quality index (AQI) reading of 345 (very poor) and was expected to stay at similar levels on Tuesday before improving to ‘poor’ on Wednesday and Thursday.