The main burn centre in Phoenix has seen its emergency department visits double, including people burning their bare feet on the scalding pavement.
Kevin Foster, director of the Arizona Burn Centre, said this June is the worst the facility has seen in 18 years.
Most patients arrive with contact burns from touching hot car interiors or walking outside without shoes.
Dr Foster said one child received contact burns after crawling through a dog door onto the hot pavement.
The burns are among several hazards resulting from a heatwave that has plagued Arizona, Nevada and California, including deaths, increased wildfire risks and a water shortage in one community.
Nevada, which is home to Las Vegas, has had at least four confirmed heat deaths since last Saturday.
California has seen at least two heat deaths, and officials throughout the state are investigating four others.
Two California firefighters were treated for heat-related injuries they received while battling a blaze in the San Bernardino Mountains near Los Angeles.
Arizona has yet to report any heat-related deaths, although Maricopa County, the most populated, had 130 heat deaths last year — a 15-year high.
Authorities declared a state of emergency in the Arizona community of Cordes Lake after its water supply dwindled amid increased consumption during the hot weather.
Officials are asking people to reduce their use, trucking in supplies from nearby Prescott Valley and cutting off water from 11pm to 3am.
Fire officials in Arizona said the extreme heat could cause more fires to pick up. Firefighters are battling at least 15 wildfires, including one that forced an evacuation and damaged at least six buildings in a town south of Tucson known for its wineries.
This article originally appeared on The Sun and has been republished here with permission.