Southern Californians living near wildfire burn areas sandbagged their homes and in some places were urged to leave them Tuesday as a storm moving in from the Pacific brought a threat of floods and mudslides.

Gov. Arnold Schwarzenegger ordered state agencies to prepare to aid local agencies in case of disaster.

"The state stands ready to help local governments protect lives and property," he said.

A low-pressure area off the coast was heading northeast and could bring an inch of rain through Thanksgiving and up to 4 inches in the mountains, said Stan Wasowski, a forecaster with the National Weather Service in San Diego.

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Flash flood watches were out through Wednesday evening for areas where grass and brush that could help prevent mudslides burned away.

Some places could get a half-inch of rain in an hour, the weather service said.

Rain began to fall Tuesday night northwest of Los Angeles in Santa Barbara County, where an evacuation order affecting at least 600 homes was issued for burned areas at risk of mudslides and floods, said county spokesman William Boyer.

A wildfire earlier this month destroyed more than 200 homes in the county and left the area vulnerable to disaster, he said.

"The fire wiped out all vegetation and the soil is very unstable," said Boyer, noting that the evacuation order would remain in effect until at least Wednesday. "... We're talking about some very steep slopes up there."

A series of wildfires stoked by Santa Ana winds damaged or destroyed about 1,000 homes in Los Angeles, Orange, Riverside, Santa Barbara and San Bernardino counties this month. Those burn areas combined equaled about 65 square miles. In addition, October wildfires burned dozens more homes and scorched the equivalent of more than 35 square miles. Other areas remain scarred from fires in recent years.

In Orange County, voluntary evacuations were in effect for three burned areas of Yorba Linda, a city of about 65,000 southeast of Los Angeles.

More than 135 members of the California Conservation Corps were sent to canyons in Yorba Linda to place sandbags and clean out culverts and spillways to handle runoff.

Heavy equipment operators placed lines of portable concrete barriers below the denuded hillsides of Chino Hills State Park to redirect potential storm flows away from Yorba Linda homes. Ninety percent of the wilderness park burned.

Some homeowners paid a private company to spray a gluey substance to protect a bare area. It contained rye seeds that would sprout in a few weeks.

"That's kind of the whole purpose of it, is to keep the soil in place until something can be germinated and get some vegetation going again," Jeff Weaver, president of Corona-based All-Preferred Hydroseed Inc., told KTLA-TV.

A call also went out for volunteers to fill sandbags in Sierra Madre, a hideaway Los Angeles suburb at the foot of a fire-stripped section of the steep San Gabriel Mountains.

City Hall was literally flying a yellow flag — the second-highest level of its mudflow forecast system — to alert affected citizens to be prepared to leave their homes because of possible small debris flows.

"After our April and May fires, we knew the next step would be mud and we started preparing right away," said city spokeswoman Elisa Weaver. "We wanted to be able to warn people to be ready."

The city established a system of green, yellow and red flags to alert residents to the possibility of dangerous mudflows.

Without the fire-related risks, rain might be appreciated in parched Southern California. Downtown Los Angeles had recorded only .27 inch of precipitation since the July 1 start of the rain year — 1.35 inches below normal for this time.