UK travellers to California are being urged to check weather updates as wildfires spread by high winds triggered a state of emergency.
As many as 180,000 residents have been evacuated from areas in northern California, with power failures affecting at least one million people.
The evacuation order covers a large area of Sonoma County, including Santa Rosa.
There are fears that the winds will spread the fires into southern California.
The US National Weather Service said a powerful windstorm was expected to create “potentially historic fire weather conditions” in the region.
Gusts had reached 90mph by Sunday morning in the hills north of Santa Rosa and up to 50mph across San Francisco’s East Bay, the forecaster said.
The Foreign and Commonwealth office said in an updated travel advisory: “The US National Weather Service has advised that an expansive high pressure system in the western USA will continue to promote favourable conditions for the spreading of wildfires from northern California into southern California.
“The greater threat is expected to focus on the Transverse and Peninsular Ranges surrounding the Los Angeles and San Diego metropolitan regions.
“If you’re in these areas, check for updates on the US National Weather Service website and follow the advice of local authorities.”