Excessive heat warnings have been issued across much of the U.S. southwest as well as southern California, where dangerously high temperatures have already led to the deaths of at least four people.
Many cities in California reported record highs Sunday and Monday with temperatures rising well above 38 degrees Celsius. The desert city of Palm Springs saw a high of 48 degrees Celsius.
Under the sizzling sun, many people fled to packed beaches, choosing to take in cooler ocean temperatures and breezes.
The heat wave fueled a massive wildfire west of Santa Barbara, located north of Los Angeles, with several other blazes burning across the neighboring states of Arizona and New Mexico.
California's power grid operators warned people to conserve electricity to counter the rising demand for air conditioning, urging consumers to wait until after dark to run major appliances.
Forecasters expect Monday to be the peak of the heat wave with temperatures dropping somewhat by Tuesday.