California has evacuated a quarter of a million people as fierce winds fan wildfires in the Los Angeles region, stretching south to the Mexican border.
At least one person has died and thousands of homes are at risk in seven counties, where fires have scorched some 240,000 acres (97,000 hectares).
Firefighters warn that the fires, which are being fanned by hot winds, will get worse in the days ahead.
Hotter temperatures and high winds are forecast for Tuesday.
At least 655 homes have been destroyed, including at least 133 homes in one mountain resort community. Thousands more homes are threatened across the region.
President George W Bush has declared a state of emergency in seven counties in California, authorising the Federal Emergency Management Agency (Fema) to tackle the fires.
About 1,500 National Guardsmen have been brought in to help firefighters.
After visiting charred homes in Malibu, Governor Arnold Schwarzenegger said it was a "tragic time" for California.
"We have... the weather conditions that are perfect for huge fires all over the state," he told reporters.
"We have a lot of wind and we have dry weather, and that's the perfect storm."
LA county supervisor Zev Yaroslavsky said emergency workers had been "stressed almost beyond the point of reason".
The ground is tinder-dry after a record summer heat wave.
In San Diego county, ambulances and school buses were used to move hundreds of people from hospitals, nursing homes and prisons threatened by advancing flames.
San Diego Fire Captain Lisa Blake said local firefighters lacked the resources to save all the homes at risk.
More than 1,500 firefighters have been battling the blazes.
A fire in the town of Potrero, near San Diego, killed one person and injured at least 10 others.
One San Diego firefighter, Mitch Mendler, said: "It was like Armageddon. It looked like the end of the world."
The fire in Malibu is thought to have been caused by a power cable that ignited after being blown over in heavy wind.
Among the buildings destroyed in the town of 13,000 residents were the famous Castle Kashan home and a Presbyterian church.
Thousands of students at nearby Pepperdine University were also evacuated.
The coastal area is home to many celebrities, including actor Mel Gibson, rock star Sting and singer Barbra Streisand.
Situation as of 8.31 pm local time, 22 October 2007:1. Harris fire:
22,000 acres consumed, 5% contained.2. Rice fire:
1,500 acres burned in San Diego county, 50 houses destroyed3. Witch fire:
145,000 acres in San Diego County. Some 500 houses and 100 businesses destroyed. 36,000 residents in Ramona evacuated4. Buckweed fire:
35,000 acres. Mandatory evacuation order of 15,000 local residents in place.5. Magic fire:
1,200 acres burned, moving towards Ventura but not currently threatening any structures.6. Ranch fire:
41,000 acres burned, 10% contained. Local evacuation orders in place.7. Canyon fire:
3,800 acres consumed. 600 houses threatened, some 1,700 firefighters deployed.8. Slide fire:
1,500 acres burned, 20 houses destroyed and 400 threatened.9. Santiago fire:
15,200 acres burned, 30% contained. Some 3,000 houses threatened in local area.
Only fires which have consumed 1,000 acres or more are listed.
Sources: Cal Fire, US National Interagency Fire Center