Parts of California, Oregon and Washington state will experience extreme heat at least through Tuesday, forecasters say.

A dangerous heat wave has descended on much of California and the U.S. Southwest, with triple-digit temperatures expected along with a higher risk of wildfires.

Red flag warnings now cover parts of Oregon, Washington and California. In Oregon and California, crews are battling flames that are burning thousands of acres. Along the West Coast, heat alerts remain in effect for 11 million people.

Ten structures — including four homes — have been destroyed by a wildfire sweeping through central Oregon as thousands of homes in the state and in Northern California wine country remained under evacuation orders Monday.

A wildfire that destroyed four homes in central Oregon was starting to stabilize on Monday, authorities said, while a blaze in Northern California wine country has so far spared some of the state's most famous vineyards.

Thousands of homes are under evacuation orders, including about 4,000 around Sisters, Oregon, because of the growing Flat fire.