Much of the western United States has baked for a third day under a punishing heat wave that has already set temperature records, prompted health warnings and strained power grids.
Although a shift in the weather has provided some relief to northern states, including Montana and Idaho, the worst is still to come for California, the National Weather Service says.
"We're in a long-duration heat wave across the Western US," meteorologist Eric Schoening said on Wednesday.
"Across the desert southwest extending into California, we're still ramping up the temperatures throughout the rest of the week."
Salt Lake City, Utah, on Tuesday tied its record high temperature since records began in 1894, at 42C.
Phoenix, Arizona, tied a record for this date at 46.1C and Needles, California, hit 49.4C, also tying a daily record.
No heat-related fatalities have been reported.
The weather service also issued red flag warnings of high fire danger in Arizona, California, Nevada and Utah, while major wildfires were burning in Colorado and Arizona.
The unusually severe late-spring heat wave was caused by a high-pressure ridge that built over southwestern deserts, the weather service said.
The heat triggered a surge in electricity demand as residents cranked up air-conditioners and fans. Power grid operators in Texas and California urged energy conservation.
The two most populous US states imposed rolling blackouts in the past year to avoid a power system collapse, California due to the heat last August and Texas in February after a deep freeze that left millions without heat.
Australian Associated Press
