SAN FRANCISCO, USA - Three people have died in a California wildfire which has forced thousands of people to flee their homes.

One of the victims was found in a car apparently attempting to flee the fires, California Highway Patrol Officer Ben Draper told reporters.

Hundreds, if not thousands, of homes and other buildings are believed to have been damaged or destroyed by the blaze northeast of San Francisco, fire officials said.

The fire has also threatened Paradise, a town devastated just two years ago by the deadliest blaze in state history that prompted a traffic jam as panicked residents tried to escape.

Other wildfires charred huge swathes of the west of the US amid gusty, dry conditions, with Washington, Oregon and Idaho also impacted.

A blast of polar air helped slow wildfires in Colorado and Montana.

Since the middle of August, fires in California have killed 11 people, destroyed more than 3,600 structures, burned old growth redwoods, charred shrubland and forced evacuations in communities near the coast, in wine country and along the Sierra Nevada.

Thick smoke choked much of the state and cast an eerie orange hue across the sky on Wednesday as thousands of people in communities near Oroville were ordered to evacuate.

Daniel Swain, a climate scientist at the University of California, Los Angeles, conservatively estimated the fire had burned about 400 square miles in 24 hours.

"The unbelievable rates of spread now being observed on these fires — it is historically unprecedented," he tweeted.

The US Forest Service, which had taken the unprecedented measure of closing eight national forests in Southern California earlier in the week, ordered all 18 of its forests in the state closed Wednesday for public safety.

In Paradise, where 85 people lost their lives and nearly 19,000 buildings were destroyed, the sky turned from black to cherry red and ash carried on strong winds rained down in a scene reminiscent of the fateful morning of November 8 2018, former Mayor Steve "Woody" Culleton said.

"It was extremely frightening and ugly," Mr Culleton said.

"Everybody has PTSD and what not, so it triggered everybody and caused terror and panic."

In Southern California, fires burned in Los Angeles, San Bernardino and San Diego counties.

People in foothill communities east of Los Angeles were warned to be ready to flee, but the region's notorious Santa Ana winds were weaker than predicted.

"We're encouraged that the wind activity appears to be dying down," Governor Gavin Newsom said. "The rest of the week looks a little more favorable."

California has set a record with nearly 2.5 million acres burned already this year, and historically the worst of the wildfire season does not begin until the autumn.

As San Francisco's skies turned deep orange, the extent of California's historic wildfires was also picked up by satellites orbiting earth.

Shocking satellite pictures have revealed the extent of California’s escalating wildfire crisis, with flames and smoke covering thousands of acres of forest visible from space.

Images shared by the US National Oceanic and Atmospheric Association (NOAA) and NASA show thick smoke covering swathes of the US’ west coast, with the haze drifting across the entire country.

The San Francisco Bay Area awoke to a disorienting sight on Wednesday morning: deep orange skies and a smoky darkness lingered hours after sunrise, serving as a stark reminder of the wildfires still raging across California.

The phenomenon ― which was also seen in Oregon on Tuesday ― is a result of 16 different fire complexes burning in the region, dispersing smoke with the help of gusty wind.  

“Strong winds over the past few days transported ash from fires in northern California and the Sierra Nevada into the region,” the Bay Area Air District, the region’s air quality control agency, explained in a tweet.

“If smoke becomes too thick in a certain area, most of the light will be scattered and absorbed before reaching the surface, which may cause dark skies.”

A thick layer of marine fog below the smoky skies intensified the effect.

The National Weather Service’s Bay Area branch warned that even though the air quality in the region was moderate on Wednesday morning, the “unprecedented smoke” hanging high in the air would likely descend closer to street level as the day went on, making the air more dangerous to breathe.

It was a familiar warning for Californians. Uncontrolled blazes across the state this year have so far burned a historic 2.3m acres, representing a nearly 2,000% increase in land burned compared with the sam time period in 2019, according to the California Department of Forestry and Fire Protection.

“This is yet another reminder though that we’re living with the effects of climate change in real time,” San Francisco mayor London Breed tweeted Wednesday morning.

Here are some images of Wednesday’s orange skies, which many compared to a scene from Mars.