A man salts a downtown sidewalk in Washington, Thursday, March 5, 2015, as snow begins to fall. The U.S. federal government said its offices in the Washington area will be closed Thursday because of a new round of winter weather expected in the region. The Office of Personnel Management said non-emergency personnel in and around Washington were granted excused absences for the day. Emergency employees and telework-ready employees were expected to work. (AP Photo/Andrew Harnik)

Hotel staff practice self-defence skills after a training session given by team member of Special Weapons and Tactics (SWAT) team, in Hangzhou, Zhejiang province, April 7, 2016. (Photo by Reuters/Stringer)

Vocalist Laila Skovmand, a musician with Danish company Between Music, plays underwater in a tank during a rehearsal ahead of their UK premiere concert Aquasonic at the Tramway in Glasgow on Ocrober 25, 2017. (Photo by Robert Perry/PA Images)

In a photo taken on July 29, 2018 instructor Kim Ju Yang (20) holds a North Korean- made assault rifle as she poses for a portrait at the Meari shooting range in Pyongyang. The Meari shooting range offers customers the opportunity to shoot a number of North Korean and foreign- made firearms, most of which have been modifed to fire .22 calibre ammunition costing one US dollar per round. (Photo by Ed Jones/AFP Photo)

Tourists walk as others relax on the beach in the Red Sea resort of Hurghada, Egypt, July 17, 2017. (Photo by Gleb Garanich/Reuters)

Salcomp players huddle at the center of the pitch of Arena da Amazonia after winning the Peladao amateur soccer tournament in Manaus, Brazil, Saturday, February 16, 2019. It is the team's second title, the first was in 2011. (Photo by Victor R. Caivano/AP Photo)

The sanctuary of Lourdes flooded, in Lourdes, southwestern France, Tuesday, June 18, 2013. French rescue services and police are evacuating hundreds of pilgrims from hotels threatened by floodwaters from a rain-swollen river in the Roman Catholic shrine town of Lourdes. (Photo by Bob Edme/AP Photo)

“Thunderstruck”. Summer stom. A super cell formed off the coast of New Zealand, intensified and swept across Christchurch and North Canterbury, February 23, 2014. Photo location: Christchurch, New Zealand. (Photo and caption by David Hardy/National Geographic Photo Contest)