Delhi is expected to record the coldest day in December on Monday in the last 119 years with a daytime temperature of 9.4 degrees Celsius, the India Meteorological Department said. As dense fog engulfed the national Capital and its adjoining areas, more than 500 flights were delayed till the afternoon.

The weather department has temperature data from 1901. The previous lowest maximum temperature in December – 11.3 degrees Celsius – was recorded in 1997. At 4.20 pm, the weather department said the record was most likely to be broken in the next three hours.

Transport services were severely disrupted because of the weather. “Around 530 flights, which includes 320 departures and 210 arrivals, were delayed till 12.52 pm,” an airport official told PTI.

Earlier in the day, airport authorities had asked passengers to contact their respective airlines for flight updates. “Owing to dense fog in north India our flights have been impacted across India,” IndiGo said in a statement. “We will continue to review the situation and provide real time updates on our social platforms.” Airlines also asked passengers to check flight status before leaving home.

At least 30 trains were delayed due to poor visibility on Monday morning. The low visibility also spelled trouble for road commuters. Six people were killed and five injured as their car skidded off the road and fell into a canal in Greater Noida on Sunday night. The accident reportedly took place due to fog, the police told PTI.

The car was on its way to Delhi. “Altogether 11 people were on board the Maruti Ertiga,” said an unidentified police official. “The car fell into the Kherli canal in Dankaur area. All 11 were taken to a hospital, where doctors declared six of them dead, while the remaining five are undergoing treatment.”

The temperature on Monday morning dropped to 2.2 degrees Celsius, according to the monitoring unit on Lodhi Road. The minimum temperature recorded at the Safdarjung observatory, which is considered the official figure for Delhi, was 2.6 degrees Celsius.

Meanwhile, the air quality in the national Capital continued to deteriorate. On Monday morning, it was in the “severe” category with the Anand Vihar observatory recording air quality index of 462 and the Okhla Phase-2 centre reporting an AQI of 494. Weather officials said that this was primarily because of a thick cloud cover over the city, coupled with low wind speed and high levels of moisture in the air.

Delhi on Sunday registered its 16th successive “severe cold day”, with minimum temperature recorded at 3.4 degrees Celsius. The maximum temperature on Sunday was 15.8 degrees Celsius, five degrees below normal. The national Capital is witnessing the longest cold spell in December in 22 years. Since 1993, Delhi has had a cold spell only in four years – 1997, 1998, 2003, and 2014. According to the weather department, a “severe cold day” is registered when the minimum temperature drops to less than 10 degrees Celsius and the maximum temperature is at least 6.4 degrees Celsius below normal. A “cold day” classification is used when the minimum temperature is less than 10 degrees Celsius and the maximum is 4.4 degrees Celsius below normal.

Weather department officials said there will be some relief from Monday as temperatures may rise by a few notches. “As we had forecast, a change in the wind direction from northwesterly to easterly has started and the reduction in the intensity of cold days and cold wave has already started from today [Sunday],” said Kuldeep Srivastava, head of IMD’s Regional Weather Forecasting Centre at Delhi, according to Hindustan Times. “This can be seen in the increase in the maximum and minimum temperatures.”

However, there could be western disturbance from December 31 that is likely to bring rain and hailstorm in parts of the Capital between January 1 and January 2. “From tomorrow [Monday] the maximum and minimum temperature will rise, but after the rainfall there will be a slight dip again,” Srivastava added.

The intense cold forced the Haryana government to order schools to remain closed on Monday and Tuesday. The India Meteorological Department on Sunday issued a red-colour warning for Delhi, and the states of Punjab, Haryana, Rajasthan, Uttar Pradesh and Bihar. Red is the highest level of warning.