Temperatures in the Southwest are expected to reach 120 to 125 degrees this week in states already struggling with multiple wildfires that have scorched tens of thousands of acres, NBC News reported.
Excessive heat warnings and heat advisories were in effect across southern California, Nevada and Arizona, affecting some 25 million Americans, the National Weather Service reported.
So far four people have died in heat-related deaths in Arizona, and a fifth was reported missing over the weekend.
It was hot enough in Arizona to fry eggs on the sidewalk, the Arizona Republic reported.
The deadly heat was also hastening separate blazes across the region. A fire in Arizona had consumed 12,140 acres by Sunday night, the United States Forest Service's information service reported. While a 7,890-acre fire in Santa Barbara, California, was 51 percent contained on Sunday night, officials said.
A new fire in San Gabriel, Calif., on Monday rapidly grew from 5 to 300 acres.