A baking heatwave that has gripped the US Southwest for three days has spread eastward to Iowa and Missouri, while punishing the hardest-hit areas with record high temperatures that have strained power systems.
The National Weather Service on Thursday issued excessive heat warnings for much of the Southwest, including Arizona, southern Nevada, much of California and southern Utah. Heat advisories were issued for parts of the Central Plains, including Kansas, Nebraska, Iowa and Missouri.
"It's a pretty big impact with respect to where the record heat is," National Weather Service meteorologist Bob Oravec said from the Weather Prediction Center in College Park, Maryland.
A high-pressure system has been parked for three days over the Southwest, a region used to temperatures of around 38C between now and September.
Salt Lake City, Utah, on Tuesday tied its all-time high temperature since record-keeping began in 1894, at 42C.
Forecasters say more records could fall on Thursday, where by late-afternoon temperatures could hit 47C in Phoenix, and 45C in Las Vegas.
California's Death Valley National Park, typically one of the hottest spots in the world, recorded 54C on Wednesday.
The National Weather Service has issued red flag warnings across the Southwest to warn of fire dangers and major blazes were burning across the region, although most of them were more than 50 per cent contained as of Thursday afternoon.
A cold front is expected to bring relief to the midsection of the country on Sunday as temperatures in the Southwest slowly moderate as well.
Australian Associated Press