Heat associated deaths in Maricopa County have hit a half-year record with 17 such fatalities reported through the first week of July and another 126 under investigation.
The higher numbers come as more homeless people live unprotected outdoors in the arid desert city of Phoenix, where summer temperatures soar well into triple digits.
Temperatures there are expected to hit 112 degrees by Friday.
Cities in other around the U.S. and the world are also sweating through earlier, more intense and longer lasting heat waves that scientists blame on global warning.
A heat wave currently grips Europe with London officials asking people to stay home and wildfires raging in France, Spain and elsewhere.