Scientists blame human-caused climate change with an extra push from El Nino, which is a temporary warming of parts of the Pacific Ocean that changes weather around the globe.
Eighteen people have died from the heat in Maricopa County so far this summer, and 69 of other deaths are being investigated as being a result of extreme heat.
For the past two years, Phoenix officials have closed some of the city’s most popular hiking trails when temperatures have soared, to cut down on the number of heat-related incidents.