California is struggling to contain huge wildfires burning forests and homes, warned Governor Gavin Newsom on Friday as more than 12,000 fire-fighters battled blazes that have killed six people.
Help was on its way from several US states as Gov Newsom put in a plea for assistance from Australia and Canada.
"These fires are stretching our resources, our personnel," he said.
Among the 560 fires are some of the largest the state has seen.
More than 12,000 dry lightning strikes started the blazes during a 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 in a day, forcing 175,000 residents to flee.
Two fires are now the 7th and 10th largest in the state's history, Gov Newsom said as he urged President Donald Trump to sign a major disaster declaration.
The worst are in the mountains to the south and east of San Francisco.
At least 43 people including firefighters have been injured, and hundreds of buildings have burned down and thousands more are threatened.
Many 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 news agency.
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 had 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 she had been forced to flee to a community centre in Vacaville but was 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 was currently sleeping in her Toyota Prius.
US 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.
Here are some key guidelines for protecting yourself against Covid-19 if you must evacuate to a shelter:
- Wash your hands often
- Keep six feet of distance from anyone not among your household
- Wear a face covering when possible, and if possible, wash it regularly
- Avoid sharing food and drinks
- Frequently disinfect your area in the shelter (including toys and electronics)
Emergency shelters are enforcing social distancing rules and mask wearing, and have even given individual tents to families to self-isolate. Some counties are seeking to set up separate shelters for sick evacuees or anyone who is found to have a high temperature.
Officials say people should consider sheltering with family and friends.
In another pandemic twist, officials also advise that people remain indoors due to the poor air quality outside.
California is also facing an electricity strain, which has caused a rolling blackout for thousands of customers. Officials have appealed for residents to use less power or risk further cuts.
In total, more than 1,205 square miles (3,121 sq km) have burned across the state.
Satellite images show smoke blanketing nearly all of California, as well most of Nevada and southern Idaho.
Big Basin Redwoods State Park, California's oldest state park and home to redwood trees that are 2,000 years old, sustained extensive damage to historic buildings.
Firefighting teams are stretched thin across the state and have been forced to work longer shifts than usual.
A volunteer firefighting corps made up of state prisoners, which has helped the state battle blazes since World War Two, has been diminished this year due to the pandemic.
President Trump blamed California for the fires, and threatened to withhold federal funding as he repeated a suggestion that was met with bemusement when he first raised it in 2018.
Speaking to supporters in Pennsylvania on Thursday, he said he had told state officials: "You gotta clean your floors, you gotta clean your forests — there are many, many years of leaves and broken trees and they're like, like, so flammable, you touch them and it goes up."
"I've been telling them this now for three years, but they don't want to listen," he said. "'The environment, the environment,' but they have massive fires again."