Pedestrians cover their face as they walk along the dusty road in Kathmandu, Nepal February 27, 2017. Nepal has forced 2,500 old vehicles off roads in its capital city of Kathmandu, part of a fight against alarming air pollution levels that have hit nine times World Health Organisation (WHO) limits. Air pollution has been a chronic problem in rapidly growing Kathmandu, which sits in a Himalayan valley and is home to more than 3mn people. (Photo by Navesh Chitrakar/Reuters)

Wizz Air's Airbus A-321 flying along the Danibe river during an air show in Budapest, Hungary, May 1, 2016. (Photo by Laszlo Balogh/Reuters)

The Mil Mi-28 N military helicopter is seen at the MAKS 2019 air show in Zhukovsky, outside Moscow, Russia, August 27, 2019. (Photo by Maxim Shemetov/Reuters)

Visitors watch as Grigory Broverman, a member of the Cryophile winter swimmers club, pours a bucket of cold water over his 6-year-old daughter Liza during a flash mob, part of a celebration of Polar Bear Day at the Royev Ruchey Zoo in a suburb of the Siberian city of Krasnoyarsk, Russia, November 29, 2015. The air temperature was around minus 5 degrees Celsius. (Photo by Ilya Naymushin/Reuters)

People wear costumes as they participate in the ancient Yule Log dragging tradition during winter solstice celebrations in Riga, Latvia, December 21, 2015. (Photo by Ints Kalnins/Reuters)

A frozen public bench is seen next to a lake side due to the heavy wind conditions in Geneva February 8, 2015. (Photo by Pierre Albouy/Reuters)

Mikhail Vasilenko, a participant from the Siberian town of Nizhny Tagil, works on an ice sculpture called “The Predator”, on the last day of the annual international festival of snow and ice sculptures “The Magical Ice of Siberia”, with the air temperature at about minus 28 degrees Celsius (minus 18.4 degrees Fahrenheit), in Krasnoyarsk, Russia, January 17, 2016. (Photo by Ilya Naymushin/Reuters)

Lindsay Knutson plays in the heavy snow with her family dog, Aspen, and daughter Flora Bejblik, 4, cq, as her husband Bob Bejblik, rear left, shovels, Tuesday, March 5, 2013 in southwest Minneapolis. The National Weather Service predicted a two-day snow total of 8 to 12 inches for much of southeastern and east-central Minnesota, including the Twin Cities. (Photo by Elizabeth Flores/AP Photo/The Star Tribune)