Much of the western United States is braced for record heat waves this week, with approximately 50 million Americans placed on alert for "excessive" temperatures, which could approach 50C (120F) in some areas.
"A prolonged and record-breaking heat wave is underway across the western US," said the US National Weather Service, with "above normal to extreme high temperatures" expected at least through the weekend.
The heat wave, which stretches like a blob over much of the western third of the US map, extends east to west from Wyoming to California, and north to south from Idaho to Arizona.
Average temperatures in the vast region are above the seasonal norm, with the arid desert states of Arizona and Nevada most likely to shatter records.
The Arizona city of Phoenix experienced temperatures of 46C on Monday but forecasters predict it could pass 47C by the end of the week, with lows in the upper-20s at night.
Las Vegas in neighbouring Nevada is suffering its most extreme prolonged heat wave since early summer 2013, according to local media, and the city by today could near its decades-old temperature record of 47.2C, set in 1940.
Authorities have opened "cooling stations" for vulnerable residents without access to air conditioning, and called on social media "influencers" to help warn the public about the impact of the sweltering heat on pets.
[5:43 PM] 107°F. We have now tied the highest temperature EVER recorded at Salt Lake City in any month of the year, in the last 147 years of records. It has only happened twice before: July 2002 and July 1960. #utwx pic.twitter.com/lySLjV748q
— NWS Salt Lake City (@NWSSaltLakeCity) June 15, 2021
The highest temperature ever officially recorded was in nearby Death Valley, at 55.2C back in 1913.
As well as warning that current temperatures are "rare, dangerous and deadly," officials fear that the heat - arriving so early in the year - could lead to deadly forest fires, aggravated by chronic drought in the American West.
Some 88% of the region is in a state of drought, including all of California, Oregon, Utah and Nevada, according to the latest government surveys.
