Visibility is reduced, deadly accidents are reported and flights cancelled in cities including the capital New Delhi.

Opaque, chilly smog blanketed northern India on Monday as low temperatures collided with hazardous levels of air pollution.

Across many cities in the region, including New Delhi, the capital, visibility was reduced to 200 metres (656 feet), according to the India Meteorological Department.

Late on Sunday, six people including two children were killed when their car skidded off the road and tipped into a canal in a suburb of New Delhi, apparently because of the poor visibility, the Press Trust of India news agency reported.

“Preliminary investigations indicate the accident took place because of low visibility due to the fog,” said local police official Akhilesh Pradhan.

With temperatures dropping to one degree Celsius (34 degrees Fahrenheit) in New Delhi, street vendors, autorickshaw drivers and the homeless wrapped themselves in hooded sweaters and blankets, and warmed their hands over small bonfires.

The city was set to register its coldest December day since 1901.

New Delhi’s notorious winter air pollution worsened the air quality index to a level 10 times higher than what the World Health Organization considers safe.

Pollution has made the air colder, mixing with moisture under low wind conditions to create low-altitude clouds stretching from eastern Pakistan to India’s eastern state of Bihar, said Rajendra Kumar Jenamani, a scientist with the India Meteorological Department.

The cold and fog were expected to continue through New Year’s Day, government weather data showed.

Flights delayed, cancelled

The conditions disrupted hundreds of flights on Monday.

At least 500 flights from Delhi’s Indira Gandhi International Airport were delayed due to dense fog on Monday and at least eight flights were cancelled, an airport authority spokesman said.

In the northeastern state of Assam, zoo authorities put heaters in enclosures to protect tigers from the bracing conditions.

“The animals are not used to this and we are taking special measures to keep the animals, particularly the old ones, warm,” Tejas Mariswamy of Assam State Zoo told AFP news agency.