Triple-digit highs were felt in Arizona, Utah, Colorado, Nevada as well as in California, where Gov. Gavin Newsom signed an emergency proclamation on Thursday over concerns regarding energy grid capacity.
To the south of Sacramento, the National Weather Service (NWS) Weather Prediction Center (WPC) announced that California's Death Valley had reached a scorching 128 degrees Fahrenheit.
The desert valley has long been the record-holder for the highest air temperature ever recorded on Earth – 134 degrees Fahrenheit recorded in 1913, though that figure is reportedly contested – and just last year the agency reported a temperature of 130 degrees Fahrenheit in Death Valley, which the World Meteorological Organization (WMO) said at the time would be the third-hottest temperature ever recorded if verified after a months-long analysis.
The all-time high for Las Vegas is 117, reached in June 2017.
In a release, the WMO noted that the extreme temperatures were part of a trend due to climate change, with heat waves "more frequent and more intense."
Climatologists and scientists continue to warn that longer duration and more severe heat waves could be "the new normal," citing dry soil from the region's "megadrought."
"When the soil is wet, heat waves aren’t so bad," the University of California, Los Angeles' Park Williams, a climate and fire scientist, told The Associated Press on Friday. "But if it’s dry, we are under extreme risk."
California's Cal Fire has warned that the state has continued to "experience an increase in wildfires and acres burned" in 2021 "compared to last year."
Real relief for millions of residents was not expected through early next week, with temperatures forecast to locally shift from the desert Southwest, California and Great Basin to the interior Pacific Northwest.
However, the NWS WPC noted that a cold front was expected east of the Rockies.
The Associated Press contributed to this report