Winds Snap Trees, Knock Out Power : Weather: Santa Anas kick up throughout Southland, setting off brush fires. Gusts of up to 50 m.p.h. are expected to continue today.

Powerful Santa Ana winds, packing gusts of up to 50 m.p.h., swept through much of Southern California on Tuesday, toppling trees, setting off brush fires and knocking out power to thousands of residents.

The National Weather Service said the strong winds, which often arrive in the fall and blow from the mountains to the ocean, will continue today throughout much of the Southland.

In Ventura County, gusts up to 50 m.p.h. knocked down power lines and caused six small brush fires, officials said.

Southern California Edison officials reported 11 power outages throughout the county, lasting from half a minute to more than two hours, and affecting about 26,880 customers.

Authorities said the fires were extinguished quickly, but firefighters were put on alert because of the extreme fire danger.

About 20,000 customers in Long Beach, Lynwood, Compton, Hawaiian Gardens, Lakewood and Cerritos also lost power temporarily.

Traffic signals in several communities failed, and streets throughout much of the Southland were strewn with palm fronds, branches and debris, authorities said.

In Orange County, 40 m.p.h. winds knocked out power to thousands of people, battering homes and prompting county fire officials to patrol acres of crisp grassland looking for fire hazards.

Because of the increased fire risk, county Fire Department officials declared a “red flag watch” Tuesday afternoon, meaning that fire officials were sending more equipment and firefighters to all reported fires, said Kathleen Cha, a Fire Department spokeswoman.

County fire officials patrolled the Santa Ana and Modjeska canyon areas--sites of previous devastating fires--looking for fire hazards. “Those are pretty hot areas,” said Jon Anderson, a hazard-reduction supervisor for the county Fire Department.

Steady winds knocked down street signs and snapped tree limbs at several locations, authorities said. In one instance, a large tree fell on the Costa Mesa Freeway near Katella Avenue, blocking three lanes of traffic, fire officials said.

About 3,200 residents of Hawthorne and Inglewood were without power as a result of the winds late Monday and early Tuesday. About 200 residents of Rolling Hills Estates also suffered power outages, Southern California Edison officials said.

In the San Fernando Valley, gusts of up to 40 m.p.h. knocked out electricity in Woodland Hills, but the wind was more a nuisance than a danger.

Firefighters blamed the winds for a small fire in Winnetka that jumped from a back-yard storage shed to the roof of a neighboring house, causing an estimated $30,000 damage.

In the Santa Clarita Valley, motorists sometimes maneuvered through swirls of dust along surface streets in dry, scrubby Canyon Country. Others swerved to avoid tumbleweeds that blew across the Golden State Freeway.

Strong winds caused brief, spotty power outages for about 5,000 customers and felled small trees that were quickly removed by city crews, Santa Clarita officials said.

Times staff writers Lorna Fernandes, Peggy Y. Lee, Julio Moran, Jeff Prugh, Somini Sengupta and Eric Young contributed to this story.