The sun came out and the maximum temperature rose to 18.8°C, the warmest the daytime has been since December 31, as an approaching western disturbance helped thin the blanket of fog that plunged the city into a grey, bitter winter since the start of the year.

The western disturbance will help cut the chill for the first half of the next week, weather scientists said on Sunday, as the India Meteorological Department (IMD) separately issued an orange alert for Punjab, Haryana, and parts of Rajasthan and western Uttar Pradesh for heavy fog and cold day conditions.

“The upper-level fog finally cleared out today, which is the major reason why Delhi experienced the first rays of sunlight in days. Upper-level fog usually does not let any sunlight penetrate, leading to gloomy cold day conditions. Delhi did not experience any cold day conditions on Sunday,” said an IMD official.

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The cold conditions will likely recede from most parts of the north-western plains, but the western disturbance could bring rain and thundershowers for Haryana, Punjab, Madhya Pradesh and parts of Rajasthan on Monday and Tuesday.

In Delhi, there could likely be a drizzle on Tuesday. The “western disturbances might cause partly cloudy skies on Monday and light rain in Delhi on Tuesday. The maximum is forecast to stay below 20 degrees throughout the week”, added the official cited above.

A second weather expert said the rains, as they typically do, could lead to a return of some cold conditions later in the week. “A cyclonic circulation is causing the western disturbances to come in. This might lead to some light rain in parts of Delhi on Tuesday, following which the Capital might experience some cold day conditions later this week,” said Mahesh Palawat, vice president of Skymet.

The conditions are a relief following a string of cold days and severely cold days, which experts said is dangerous for elderly people. The Capital and its surrounding cities extended winter breaks at schools for younger grades for several days, and moved classes to start later for more senior students.

A western disturbance is a stormy system that originates in the Mediterranean Sea before sweeping towards the east and halting at the Himalayan ranges. In the northern plains, it brings rains and causes a change in wind directions. But in the mountains, it triggers snowfall. Once a western disturbance retreats, winds change back to their natural northerly direction, bringing in icy cold air from the snow-capped mountain ranges.

IMD officials also added, “Partly cloudy sky will be seen on Wednesday, with shallow to moderate fog in the morning. It might clear up by Thursday and skies will be mostly clear.”

This could mean sunny days, but with clear skies, the night temperatures — or the minimum — will likely plummet to low single digits.

On Thursday, the minimum was 8.2°C, a notch higher than usual.

“After rain stops and the WD moves away, temperatures are expected to drop again and we can expect cold wave conditions to set in over parts of northwest India,” said M Mohapatra, director general, IMD.

The minimum temperatures are in the range of 6-9°C over Punjab, Haryana, Chandigarh, Delhi, west Uttar Pradesh and north Rajasthan; 10-12°C over parts of east Uttar Pradesh, rest of Rajasthan and northwest Madhya Pradesh. It is above normal by 1-3°C in isolated pockets over Punjab, Haryana, Chandigarh, Delhi, Rajasthan and in many pockets over west Uttar Pradesh and west Madhya Pradesh, and 4-7°C above normal over many parts of east Uttar Pradesh, east Madhya Pradesh, Bihar and Jharkhand. On Sunday, the lowest minimum temperature over plains, of 3.8°C, was recorded at Alwar in east Rajasthan.

On Sunday, very dense fog (with visibility less than 50 metre) was reported from pockets over Jammu Division, Punjab, north Haryana, Chandigarh, west Uttar Pradesh, Bihar, west Rajasthan and north Chhattisgarh.

Dense to very dense fog conditions are very likely to prevail in night/morning hours in some parts of Punjab and in isolated pockets of Haryana-Chandigarh between January 7 and 9.

The IMD also warned that the western disturbance will impact areas in the Western Himalayas. “Under its influence and its interaction with lower level easterly winds, light isolated rainfall/snowfall likely over Jammu-Kashmir-Ladakh-Gilgit-Baltistan-Muzaffarabad, Himachal Pradesh, Uttarakhand on January 9 and over plains of northwest India and Central India on January 8 and 9. Light to moderate rainfall accompanied with thunderstorms and lightning very likely at some places over Maharashtra during January 7 to 9 and over Gujarat on January 8 and 9. Isolated hailstorm also likely over East Rajasthan on January 8 and 9 and over West Madhya Pradesh on January 8,” the agency said in its advisory.