Every year since 2016, the number of people in Maricopa County who have died from heat-related causes has risen to a new high. The county’s preliminary report on heat deaths from 2023, released Wednesday, confirms last summer’s extreme temperatures led to another record-breaking death toll. 

The preliminary report shows an unprecedented 645 heat deaths last year. That’s a 52% increase from the previous year and a more than 700% increase from just a decade earlier.

The dramatic rise in heat deaths in recent years has correlated with fast growth of the region’s homeless population. Most of the county's heat deaths last year occurred outdoors, and the largest share of deaths was among people experiencing homelessness.

About a quarter of last year's heat deaths occurred indoors. In 85% of those cases, the air conditioner was not working. In other indoor cases, air conditioning was not present or not in use. 

Maricopa County reports it has hired a new heat relief program coordinator heading into this summer. The state of Arizona also recently announced a new chief heat officer and statewide cooling center coordinator.

More stories from KJZZ

• 2023 will be a record year for heat-related deaths, in spite of spending to prevent it
• The hottest overnight temperatures in Phoenix history raise public health concerns