Patients are showing up at medical facilities throughout the region with burns contracted from something as simple as walking barefoot or opening a door.

One Las Vegas doctor tells the Wall Street Journal that one-third of the patients in the burn unit at his facility are there from pavement burns. Asphalt and sidewalks can reach temperatures as high as 170 degrees on a hot day. Door handles can reach unsafe temperatures as well.

While many of the cases are blisters, some are much more severe. One patient who spent just a few minutes barefoot outside ended up with a third-degree burn that required a skin graft and two hospitalizations.

At particular risk are people who pass out from the heat, landing on the sidewalk or street, particularly the elderly.

The Arizona Burn Center, meanwhile, reports it has hospitalized 50 patients with contact burns related to the heat wave. Two have died.

Temperatures in Phoenix have topped 110 degrees for 25 consecutive days, a U.S. record. And that streak isn’t likely to end soon. The National Weather Service has extended an excessive heat warning through Thursday for the city. Parts of Colorado, Texas, Oklahoma, and Wyoming have also set heat records in recent weeks. More than 46 million people remain under heat alerts as of Wednesday morning.

A report from the Center for American Progress earlier this month estimated that the cost of the extreme heat works out to an average of an extra $1 billion in health care-related costs in the United States each summer. That’s in part due to additional emergency room visits and hospital admissions for heat-related and heat-adjacent maladies.

“Hot summer days have always posed a risk of health complications, but climate change is causing an increase in prolonged periods of extreme heat,” the group wrote. “With this has come a rise in incidences of heat-related illness, as more Americans experience health complications and need to seek medical care.”