Excessive heat warnings have been issued for Los Angeles, Las Vegas, Phoenix and Tucson as dangerously high temperatures have forced residents to seek cover from the sun.
Monday was expected to be the hottest day of the heat wave, with temperatures likely to top 120 degrees in some areas.
Temperature records were shattered Sunday in dozens of cities in New Mexico, Arizona, Nevada and California.
On Sunday Yuma, Arizona, hit 120 degrees; Phoenix hit 118 degrees; Palm Springs, California, reached 118 degrees; and Burbank, California, reached 109 degrees. Previous records were matched in Albuquerque, New Mexico, at 03 degrees, and North Las Vegas, at 109 degrees.
In Phoenix, it was hot enough to cook an egg.
Four people are dead in Arizona from the heat. Two hikers died Sunday in Pima County, Arizona, from heat-related illnesses, the Pima County Sheriff's Office said. A 28-year-old trainer died from heat exhaustion Sunday after mountain biking at the Phoenix Mountain Preserve, according to the Phoenix Fire Department. A man died of heat exposure after hiking the Superstition Mountains on Saturday, the Pinal County Sheriff said.
The extreme heat also hindered firefighters trying to contain large blazes in New Mexico, Arizona and California.
The record heat even affected plane travel. A United Airlines flight operated by Mesa Airlines departed Houston's George Bush Intercontinental Airport on Sunday afternoon and was minutes away from landing at Sky Harbor Airport in Phoenix when the flight crew notified passengers it would be turning back; because of excessive heat's effects on aircraft equipment, it is against the law for planes to take off or land in temperatures of 120 degrees or higher.