A tourist walks inside the Ice Palace glacier hollow at Hintertux glacier, located at around 3250 meters above sea level, in Zillertal, Austria, 02 March, 2016. The hollow's temperature remains constant at 0 degrees Celsius, in summer and winter alike, and is also used by the University of Innsbruck for scientific research projects. (Photo by Lisi Niesner/EPA)

A combination photo shows various popular street foods under $6 from various hawker food stalls and eateries in Singapore, taken between July 28 to 31, 2016. Top row (L to R) bak chor mee, soya sauce chicken; Middle row (L to R) laksa, hokkien mee, nasi lemak, ice kachang; Bottom row (L to R) rojak, roti prata and satay. (Photo by Edgar Su/Reuters)

A woman eats an ice cream as people sunbathe on the beach in Barcelona, Spain, Friday, January 26, 2024. Spain's weather agency says recent abnormally high temperatures for this time of year are set to continue in many parts of Spain on Friday and over the weekend, with an almost summer-like feeling in many coastal areas as people take to the beaches to sunbathe and some to have a winter swim. (Photo by Emilio Morenatti/AP Photo)

The twin lighthouses of St Joseph on Lake Michigan have been transformed by a winter storm. Ice encases the buildings, giant icicles hang from the piers and the beach is frosted white. Here: Huge icicles hang from the pier. (Photo by Mike Kline/Barcroft Media)

“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)

A competitor in fancy dress emerges from muddy water during the Tough Guy Challenge endurance race on January 29, 2012 in Telford, England. Every year thousands of people run the 8 mile assault course which involves freezing temperatures, fire and ice. (Photo by Michael Regan/Getty Images)

The picturesque Zao Ski Resort, one of Japan's oldest and most popular ski destinations, is illuminated on February 10, 2007 in Yamagata Prefecture, Tohoku region of Honshu island, Japan. Coniferous trees such as the Aomori white fir lie covered with chrystallised ice and snow (described as “silver frost” or “snow monsters”) and attract visitors. (Photo by Koichi Kamoshida/Getty Images)