Dan Copeland, left, and Alex Morneau of Biddeford, Maine, former high school cheerleaders, perform back flips while enjoying the record breaking heat, Thursday, May 18, 2017, at Old Orchard Beach, Maine. The temperature climbed well into the 90s in many locations throughout the state. (Photo by Robert F. Bukaty/AP Photo)

Two hippopotamus are fed with pumpkins at the Hanoi Zoo, in Hanoi, Vietnam, 25 October 2018. The zoo has been the home for more than 800 animals of over 90 different species, including three hippopotamus, since it was built in 1976. (Photo by Luong Thai Linh/EPA/EFE)

Participants in costumes attend the first day of the annual Wave-Gotik Treffen, or Wave and Goth Festival, on May 17, 2013 in Leipzig, Germany. (Photo bilderkiste)

A Burlesque performer onstage during the London Tattoo Convention at the Tobacco Docks, in London, Britain, 24 September 2017. (Photo by Facundo Arrizabalaga/EPA/EFE)

An employee sorts waste at the Wecycler recycling centre in Ebutte Meta district in Lagos, Nigeria July 28, 2016. (Photo by Akintunde Akinleye/Reuters)

Fisherwomen laying barrels with salt in preparation for herring curing, 1937. (Photo by Topical Press Agency)

In this November 26, 2018 photo, men run during 100 meters athletics competition of the second edition of the Panamanian indigenous games in Piriati, Panama. These games were held in the Embera town of Piriati, some 55 miles (90 kilometers) east of Panama City. (Photo by Arnulfo Franco/AP Photo)