California has continued to burn, this time in the northern section of the state where a city fire has destroyed 10 houses, several downtown business offices, and forced some 4,000 people to flee their homes.

The Clayton fire in the small town of Lower Lake, 90miles (145km) north of San Francisco, spanned a major roadway and tore into the downtown area, where it consumed the post office, a winery, businesses and a Habitat for Humanity office where staffers had been raising funds to rebuild 1,300 area homes destroyed by a deadly wildfire just a year ago.

Emergency workers scrambled to transfer several patients from a hospital in nearby Clearlake to another hospital 25 miles away, AP reported.

Houses burned on both sides of Highway 140 in the area and propane tanks exploded, spewing balls of fire. Firefighters and volunteers rushed to rescue animals left behind, as tractors and utility poles burned and bumpers melted off cars.

The blazes were particularly hard to control because of extremely high temperatures, and gusty hot winds.

Firefighter reinforcements came from as far away as San Francisco.

The state's five-year drought has triggered an early start for California's customary fire season and has made blazes bigger and more powerful.

Huge, explosive fires have ripped through dried-out or difficult-to-reach areas across California this summer, such as a blaze near the famous Big Sur coastline which has burned 113 square miles (344 sq km) since late July and destroyed nearly 60 homes. It's still only contained by about 60%.

Firefighters also grappled with another major blaze farther south some 180 miles north of Los Angeles which set 12 homes alight.

And in Los Angeles, dry conditions, high temperatures and gusty winds set the stage for high fire danger in that city.