Men cover their heads from the sun while riding on a motorcycle during a hot day in Cairo, Egypt, August 17, 2015. A heatwave killed at least 61 people across Egypt from Sunday to Tuesday and caused nearly 600 people to be admitted to hospital, Egypt's health ministry said on state news agency MENA on Wednesday. (Photo by Amr Abdallah Dalsh/Reuters)

Firefighters attempt to put out a fire at an abandoned building with the protection of St. Louis City Police in St. Louis, Missouri August 19, 2015. Police fatally shot a black man they say pointed a gun at them, drawing angry crowds and recalling the racial tensions sparked by the killing of an unarmed African-American teen in nearby Ferguson, Missouri, just over a year ago. (Photo by Lawrence Bryant/Reuters)

This combination of August 30, 2005 and July 29, 2015 aerial photos shows downtown New Orleans and the Superdome flooded by Hurricane Katrina and the same area a decade later. Katrina's powerful winds and driving rain bore down on Louisiana on August 29, 2005. The storm caused major damage to the Gulf Coast from Texas to central Florida while powering a storm surge that breached the system of levees that were built to protect New Orleans from flooding. (Photo by David J. Phillip/Gerald Herbert/AP Photo)

First graders of a cadet's lyceum attend a ceremony to mark the start of the new school year in Kiev, Ukraine, September 1, 2015. September 1 marks the start of a new academic year for students in Ukraine.(Photo by Valentyn Ogirenko/Reuters)

A child plays beside an idol of the Hindu god Ganesh, the deity of prosperity, the day after it was immersed in the Yamuna river for the Ganesh Chaturthi festival in Delhi, India September 6, 2017. (Photo by Cathal McNaughton/Reuters)

Bluebella Lingerie advertising photo shoot, Oxford Circus, London, Great Britain on September 14, 2017. Bluebella has staged its most daring lingerie campaign yet, sending 19 models to strut their stuff in skimp smalls on one of London's busiest junctions. Bluebella organised the show early in the morning to minimise congestion ahead of London Fashion Week which starts on Friday 15th September. The “models” included a medical PA, a company boss, four students, two actors, a musician and two writers. (Photo by Cavendish Press/LESAUVAGE/Bluebella)

On September 1, 2004, Chechen militants stormed an elementary school in the town of Beslan in the Russian republic of North Ossetia. They took 1,100 teachers, children, and their relatives hostage, demanding the withdrawal of federal forces from Chechnya as a condition for their release. On September 3, 2004, Russian security forces stormed the building, resulting in a battle in which more than 330 hostages died, including 186 children. Here: A man assists two young hostages who managed to escape from the school building after special forces entered the school in Beslan, North Ossetia, Friday 03 September 2004. (Photo by Yuri Kochetkov/EPA)

Municipal workers try to retrieve the lid of a manhole to prevent pedestrians from falling in, in Mumbai, India, Wednesday, September 20, 2017. Incessant rainfall in India's commercial capital has affected air and rail traffic, and schools and colleges remained shut for the day. (Photo by Rafiq Maqbool/AP Photo)