Fire crews at a blaze in the wine country north of San Francisco were on high alert Friday as forecasters warned of extreme fire danger into Saturday.
Smoke rose along the road and on hillsides, where crews of firefighters could be seen attacking pockets of flame with picks, shovels and hoses.
The fires that began Sunday in the famed Napa-Sonoma wine country about 45 miles north of San Francisco came as the region nears the third anniversary of deadly wildfires that killed 22 people.
The wildfires racing across the tinder-dry landscape in California, Idaho, Oregon and Washington are extraordinary, but the long reach of their smoke isn't unprecedented.
The flames have destroyed neighborhoods, leaving a barren, gray landscape in their wake, driven tens of thousands of people from their homes and cast a shroud of smoke over the region.
A fire approaching Molalla triggered a mandatory evacuation order for the community of about 9,000 people 30 miles (48 kilometers) south of Portland.
In Southern California, fires burned in Los Angeles, San Bernardino and San Diego counties, and the forecast called for the arrival of the region's notorious Santa Anas.
Sometimes the made-for-social-media gatherings are spectacles and include explosives and even guns, and at least one had deadly consequences.
Smoke from the fires made the region's air quality dangerous, forcing people to stay inside.
Three major collections of fires, dozens in all, carved their way on Thursday through forests, canyons and rural areas in the San Francisco Bay Area and central California.
Officials allowed flames to run up the side of Mount San Gorgonio, an 11,000-foot (3,350-meter) peak, because it wasn't safe to let crews work in such steep, rugged terrain.
The wildfires have hospitalised hundreds, and charred about 170,000 acres of land, destroyed at least 3,500 structures and forced nearly 20,000 residents to evacuate.
US President Donald Trump declared a major disaster in California, freeing up federal funding and resources to help fight the 17 large wildfires in the western state.
Fanned by winds of over 50 miles (80 kilometers) an hour, the blazes have forced more than 20,000 people to evacuate in the country's heaviest populated state since they began Sunday night.