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

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.

Dangerously hot conditions hit states up and down the West Coast over the weekend, owing to a persistent heat wave stretching from the Pacific Northwest to California and the desert Southwest.

Multiple wildfires have already erupted in parts of the western United States, including in Oregon and California's Napa County.

Two major wildfires in California and Oregon force mass evacuations as firefighters battle blazes amid dangerous heat conditions.

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.