Record high temperatures are expected to bake the American Southwest as a potentially deadly heat dome covers the region this week.
The National Weather Service issued a series of urgent warnings Tuesday morning about "dangerously hot conditions" forecast through Friday.
More than 17 million people live in areas covered by the extreme weather alerts, according to CNN.
Triple-digit temperatures are expected in many areas, even though the official start of summer isn't until June 20.
"It does seem like Mother Nature is turning up the heat on us a little sooner than usual," Tiffany Davila, spokesperson for the Arizona Department of Forestry and Fire Management, told the Associated Press.
What is a heat dome?
A heat dome is a mass of exceptionally hot air created when high pressure in the atmosphere prevents warm air from rising, creating a virtual bubble that covers the affected area, according to the American Meteorological Society.
Conditions inside a heat dome are compounded by a phenomenon known as subsidence, in which the high pressure causes drives temperatures even higher by compressing the surface air, according to the society.
The impact can be deadly, especially in regions that don't often experience very high temperatures.
In 2021, a heat dome over the American northwest, western Canada and Alaska killed more than 650 people and stressed hospitals that were overrun by heat-related emergencies.
What states will be affected?
The National Weather Service warnings cover parts of Arizona, California, Nevada, Texas and Utah.
In northern California, where about 475 firefighters were still battling a wildfire that erupted Saturday west of San Francisco, the excessive heat warning was set to go into effect at 11 a.m. PT Tuesday and continue through 8 p.m. PT Thursday.
For most of the other areas, the warnings run from 11 a.m. PT Wednesday to 8 p.m. PT Friday.
Where will it be the hottest?
The odds are good that the thermometer will hit 114 degrees in Las Vegas, where the temperature on the Strip was 86 degrees Tuesday morning.
Afternoon highs of up to 113 degrees are predicted in Phoenix, which struggled through 31 consecutive days of at least 110 degrees last summer.
The heat wave also could push the mercury to 122 degrees in Death Valley National Park, where the National Park Service says a high air temperature of 134 degrees was recorded at Furnace Creek on July 10, 1913.
"As the heat builds day by day there will be little relief during the overnights, especially within the Las Vegas Valley and Death Valley National Park," the National Weather Service said.
