A severe cold wave in north India is leaving millions shivering, with the national capital New Delhi recording its coldest December day since 1901.
The maximum temperature recorded at Safdarjung in the city was 9.4 degrees Celsius at 2.30pm (Indian time) on Monday, according to the India Meteorological Department (IMD).
Delhi's previous coldest day in the month was on Dec 28, 1997 when the maximum temperature dropped to 11.3 deg C. The city was engulfed in dense fog on Monday morning, affecting flights and rail services.
Cold conditions have been continuing in the northern parts of India since the middle of last month, with minimum temperatures dropping below 5 deg C at several places in Rajasthan, Punjab, Delhi, Haryana, west Uttar Pradesh and north Madhya Pradesh.
In Uttar Pradesh, 59 people have reportedly died due to the intense cold wave though the state government maintains that the deaths were due to health-related conditions.
The severe cold wave conditions continued for the third day in most parts of Madhya Pradesh on Monday with two deaths reported from Shivpuri and Harda districts. With rain forecast for a couple of days from Tuesday, the state is likely to experience a further drop in temperature.
Every year, in the second half of December and the first half of January, temperatures routinely drop up to 4 deg C at some point of the day in many places in north and northwest India.
In December, the maximum daily temperature does not rise beyond 18 deg C in most of Punjab, Haryana, Himachal Pradesh and western Uttar Pradesh. In Delhi and northern Rajasthan, daily maximum temperatures are usually not above 22 deg C for most of December.
However, this winter, in many parts of the region, maximum temperatures on some days have been nearly 10 deg C below normal.
In Delhi, the average maximum temperature for December was less than 20 deg C until Dec 27. This has happened only four times in the last 118 years.
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 Delhi, visibility was reduced to 200 metres, according to the IMD.
Six people 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 reported.
With temperatures dropping in New Delhi to 1 deg C, street vendors, auto rickshaw drivers and people who sleep on the streets wrapped themselves in hooded sweaters and blankets and warmed their hands over bonfires.
The fires worsened Delhi's notorious winter air pollution, with the air quality index - a measure of ozone, carbon dioxide and particulate matter - topping 500 at a monitor at the US Embassy, 10 times what the World Health Organisation 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 Dr Rajendra Kumar Jenamani, a scientist with the IMD.
The cold and fog are expected to continue until the first week of January as an unusual and powerful spell of "Western Disturbances", originating in the Mediterranean Sea, has made the Hindi heartland shiver for the past fortnight.
"It is a long spell, very unique in nature, and would affect entire northwest India," said Dr Jenamani.
The thick cover of smog on the Indo-Gangetic plains and the uneven warming of the Indian Ocean has a role to play in this robust spell of Western Disturbances, the extratropical storms originating in the Mediterranean region causing sudden winter rain in the northwestern parts of the Indian subcontinent, which have brought the day temperatures in some Indian cities to below 12 deg C.
Top scientists fear that due to climate change, such harsh and unexpected weather conditions will continue to trouble people.
"The climate change affecting the intensity and frequency of Western Disturbances can bring mercury down in the northern region in the years to come, while central and southern India could be warmer," said Dr Bhupinder B. Singh, senior scientist at the Centre for Climate Change Research in Pune.
He added that change in land use and land cover, which are shrinking the forest belt, are among the few causes for climate change.
Besides, greenhouse gases, fine dust particles in the air, are making conditions worse.
Indo-Asian News Service, Reuters