In this picture taken on December 13, 2017, a woman commutes on a street on a cold day in Baoding. As temperatures dipped below freezing in a northern Chinese village, a group of parka-clad women tried to stay warm as they played mahjong around a small gas stove in a grocery store. (Photo by Fred Dufour/AFP Photo)

A young visitor interacts with a baby hippopotamus swimming in its enclosure at the Berlin Zoo on January 1, 2018. Tourists and locals flocked to the zoo in the German capital on the unseasonably warm first day of the year. (Photo by Odd Andersen/AFP Photo)

Members of a samba school warm up before parading along Copacabana Beach in Rio de Janeiro, Brazil, Saturday, January 6, 2018. Musicians and members from Rio de Janeiro's top 13 samba schools have paraded in an event aimed at promoting tourism ahead of Rio's world famous Carnival that begins early next month. (Photo by Leo Correa/AP Photo)

An Indian student warms up during the 44th Samartha Summer Sports Coaching Camp organized by Shree Samarth Vyayam Mandir in Mumbai, India, 25 April 2018. Mallakhamba arose in the western state of Maharashtra centuries ago. It was originally practiced by wrestlers and soldiers as a strength training exercise. (Photo by Divyakant Solanki/EPA/EFE)

A girl stretches next to a pram on the embankment of the Moskva river in Moscow on October 18, 2018. The European part of Russia enjoys an unusually warm weather for the season with temperatures reaching up to 22 degrees centigrade. (Photo by Mladen Antonov/AFP Photo)

A cat walks in front of the body of a man killed by unknown gunmen in Manila, Philippines early October 18, 2016. A sign on a cardboard found near the body reads, “Pusher Ako, Wag Tularan”, which translates to “I am a (drug) pusher, don't be like me”. (Photo by Damir Sagolj/Reuters)

Puerto Rico's Grace Claxton warms up before competing in the Women's 400m Hurdles Round 1 during the athletics event at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 15, 2016. (Photo by Jewel Samad/AFP Photo)

A mother bear takes a dip in the water to cool off in the warm summer sun but refuses to leave her three youngsters behind – so they climb aboard her back. (Photo by Jon Langeland/Solent News & Photo Agency)