Delhi experienced the heaviest fog of the season between Monday night and Tuesday morning as a portion of the haze extended from Punjab all the way across the Indo-Gangetic plain.
From Monday night from 10 p.m. to Tuesday morning at 4 a.m., the fog caused visibility at Delhi's Indira Gandhi International Airport to drop to 50 metres, delaying about 100 flights. Between 11 p.m. and midnight on Monday, five additional flights were diverted to Jaipur, according to airport officials.
Over the previous few days, the northern regions of the nation have had poor visibility.
RK Jenamani, a scientist with the India Meteorological Department (IMD), claimed that poor visibility at most airports caused flight operations to be disrupted from 6 p.m. on Monday to 1 p.m. on Tuesday.
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“The fog covered nearly 1 million sq km in area, covering north, central, and eastern India. It was nearly three times more area on Monday night and Tuesday morning. The visibility stayed between 50 to 100 metres between 10 pm on January 2 and 4 am on January 3," the HT quoted him.
Around 11.25 p.m. on Monday, the SpiceJet flight from Jabalpur to Delhi was reported as having been diverted to Jaipur in the nation's capital.
A GoFirst flight from Mumbai to Delhi (G8 341) was diverted at 11.36 p.m.
Two other flights—a Dubai-Delhi flight (VTVRV) and an Air India flight from Ahmedabad to Delhi—were diverted at 11.35 p.m. and 11.36 p.m., respectively (AI 816).
The Delhi airport tweeted at 10:10 p.m. that low visibility protocols were in place and advised travellers to check with the airlines for the most recent flight information even though no flights had been impacted up until that point.
According to IMD, Delhi experienced a "cold day" on Tuesday as cold winds from the Himalayas swept across the plains.
The Tuesday fog caused at least 21 trains to Delhi to be delayed by one and a half to five hours.
When visibility falls below 1,000 metres, IMD describes a fog as "shallow," as "moderate," between 200 and 500 metres, and as "dense," below 200 metres. When visibility is less than 50 metres, the air is "extremely dense."
IMD predicts that for the next four days, Delhi's maximum temperature will be about 17°–18°C, while the city's minimum temperature will steadily drop starting on Wednesday and is expected to reach 4°C by Friday.