The average annual temperature in Phoenix increased by 4.4 degrees from 1970 to 2023, according to a new analysis by Climate Central.
Why it matters: A 4-degree temperature difference can be a matter of life or death during the summer.
645 people died of heat-related causes in Maricopa County during last year's historically hot summer. More than half of the deaths occurred on the 21 days the National Weather Service calculated an extreme heat risk.
Zoom out: All 50 states and nearly all 241 U.S. cities the group analyzed have warmed since 1970.