Maricopa County has confirmed 331 heat-associated deaths this year. There were 295 as of last week.
While this July was the hottest on record in the Valley, Sonia Singh with the County Department of Public Health says multiple factors lead to heat illness and death.
"It can be both the really long period of extreme heat that we had as well as the high low temperatures that we were experiencing. That really doesn't give people a chance to cool off if they don't have another place to go to cool off from the heat," Singh said.
There are still 273 deaths under investigation.