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.
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.
While there are only small pockets in the southeastern U.S. that are haze free, experts say the smoke poses less of a health concern for those who are farther away.
This year's blazes have taxed the human, mechanical and financial resources of the nation’s wildfire fighting forces to an extraordinary degree.
Data collected by the EU's Copernicus Atmosphere Monitoring Service found smoke from the fires had traveled 8,000 kilometers through the atmosphere to Britain and other parts of northern Europe.
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.
The FBI said it worked with local authorities to investigate claims that extremists set wildfires and found them to be false.
Some other states only allow journalists behind fire lines with escorts, while others rarely grant permission for reporters to get anywhere near an active wildfire, saying that safety is paramount.
The state's emergency management director, Andrew Phelps, said officials are “preparing for a mass fatality event” and that thousands of structures have been destroyed.
People evacuated statewide because of fires had climbed to an estimated 500,000, more than 10 percent of the 4.2 million people in the state.
Smoke from the fires made the region's air quality dangerous, forcing people to stay inside.