The waning moon sets behind leafless sumac trees on a crisp, clear morning, Thursday, December 15, 2016, in Portland, Maine. Much of the northern Mid-Atlantic and Northeast will stay cold for the next couple of days as the arctic air remains stuck over the northern Appalachians, the National Weather Service said. (Photo by Robert F. Bukaty/AP Photo)

A man stands on a jetty on the fog-shrouded Victoria Harbour Wanchai in Hong Kong, China, 22 March 2022. Fog is common in Hong Kong in spr​ingtime when the territory is affected by alternate cold and warm air. (Photo by Jerome Favre/EPA/EFE)

Vendor Yegor Dyachkovsky, 45, poses for a picture at an open-air market on a frosty day in Yakutsk, Russia, January 15, 2023. Yakutsk, one of the Russia's north-most cities, is hit by an extreme cold snap as the air temperature on Sunday (January 15) plunged as low as minus 51 degrees Celsius (minus 59.8 degrees Fahrenheit). (Photo by Roman Kutukov/Reuters)

“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)

Visitors watch as members of a local winter swimmers club pour buckets of cold water over their daughters, 7-year-old Liza Broverman and 2-year-old Alisa Smagina during a celebration of Polar Bear Day at the Royev Ruchey zoo, with the air temperature at about minus 5 degrees Celsius (23 degrees Fahrenheit), in Krasnoyarsk, Russia, November 27, 2016. (Photo by Ilya Naymushin/Reuters)

Children pour cold water on themselves under the control of fitness coach Margarita Filimonova (R) at local kindergarten number 317, with the air temperature at about minus 23 degrees Celsius (minus 9.4 degrees Fahrenheit), in Russia's Siberian city of Krasnoyarsk, February 5, 2013. (Photo by Ilya Naymushin/Reuters)

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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)

Swans swim over a lake, with the air temperature at about minus 35 degrees Celsius (minus 31 degrees Fahrenheit) as steam ascends above the water during sunset near the village of Urozhainy, Sovetsky district of Altai region, January 26, 2015. About 600 swans annually migrate to the lake, which is heated by warm springs, where they spend their winter being fed by yagers, which helps them to survive the severe cold. (Photo by Andrei Kasprishin/Reuters)