The Doppler on Wheels (DOW) vehicle scans a supercell thunderstorm during a tornado research mission, May 8, 2017 in Elbert County near Agate, Colorado. Doppler on Wheels (DOW) is a mobile doppler radar mounted on a truck that brings instruments directly into storms, allowing scientists to scan storms and tornadoes and make 3-D maps of wind and debris. (Photo by Drew Angerer/Getty Images)

A police officer stands at a police cordon near the scene of a terror attack in London, U.K., on Sunday, June 4, 2017. A van swerved into Saturday-night crowds on London Bridge, before three men got out and went on a stabbing rampage through nearby bars. (Photo by Luke MacGregor/Bloomberg)

In this January 27, 2019, photo, Hindu holy men of monastic order Juna Akhara participate in a ritual before becoming Naga Sadhus or naked holy men at Sangam, the confluence of three holy rivers during the Kumbh Mela or pitcher festival in Prayagraj Uttar Pradesh state, India. At every Kumbh, including this year's, thousands of devotees were initiated into the reclusive sect of the Naga Sadhus, naked, ash-smeared cannabis-smoking Hindu warriors and onetime-armed defenders of the faith who for centuries have lived as ascetics in jungles and caves. (Photo by Rajesh Kumar Singh/AP Photo)

Girls during a class at the Teire Irish dance school in Moscow, Russia on March 15, 2019. (Photo by Sergei Karpukhin/TASS)

In this April 16, 2019 photo, people wait to be given empty water containers and water purification pills during the first aid shipment from the Red Cross in Caracas, Venezuela. In late March, the Red Cross federation announced it would soon begin delivering assistance to an estimated 650,000 people and vowed that it would not accept interference from either side of the polarized country. (Photo by Ariana Cubillos/AP Photo)

Mil Mi-8 combat helicopter flies over Moscow, Russia on May 7, 2019 during the dress rehearsal of a Victory Day air show marking the 74th anniversary of the victory over Nazi Germany in the 1941-1945 Great Patriotic War, the Eastern Front of World War II. (Photo by Sergei Savostyanov/TASS)

A woman carries her son in a bucket after collecting water from a municipal water tanker on the outskirts of Chennai, India, July 4, 2019. (Photo by P. Ravikumar/Reuters)

An annual fire festival is held in Nachikatsuura, Wakayama Prefecture, western Japan, on July 14, 2019. (Photo by Kyodo News via Getty Images)