California is struggling to contain huge wildfires burning forests and homes warned Governor Gavin Newsom on Friday as more than 12,000 fire-fighters battle the blazes that have killed six people.
Help is on its way from several US states as Gov Newsom put in a plea for assistance from Australia and Canada.
Among the 560 fires are some of the largest the state has seen.
More than 12,000 dry lightning strikes started the blazes during an historic heat wave in which thermometers in Death Valley National Park reached what could be the highest ever temperature reliably recorded.
By Friday, emergency officials said some of the fires had doubled in size from the day earlier and have now forced 175,000 residents to flee.
Two of the fires are now the 7th and 10th largest in the state's history, Gov Newsom said as he urged President Trump to sign a major disaster declaration.
The worst are in the mountains to the south and east of San Francisco.
Many of the blazes are burning on steep, difficult-to-access terrain and have been fuelled by strong winds. The fires are also threatening larger towns including Santa Cruz where flames reached within a mile of the University of California Santa Cruz campus, reports Reuters.
More fire-fighters, engines and surveillance planes are racing in from other states including Oregon, New Mexico and Texas to help. Assistance from what Gov Newsom called "the world's best wildfire-fighters" in Australia has been requested.
"We simply haven't seen anything like this in many, many years," he said, adding that an area the size of the US state of Rhode Island has already burned within California.
With more than 650,000 coronavirus cases, California also has the highest number of infections in the US, and some evacuees have said they are afraid to go to emergency shelters.
One woman told CNN that she was forced to flee to a community centre in Vacaville, but is refusing to go inside for fear of catching coronavirus.
"Not only are we dealing with Covid, but with also the heat and now the fires," said Cheryl Jarvis, who said she is currently sleeping in her Toyota Prius.
US disaster agencies have updated disaster preparedness and evacuation guidance in light of Covid-19. People who may be required to flee have been to told to carry at least two face masks per person, as well as hand sanitiser, soap and disinfectant wipes.