High Winds Fan Flames That Scorch Many Homes : Fires: More than a dozen houses are burned in blazes around the Southland. The dangerous weather conditions are expected to last through the week.

Strong Santa Ana winds gusting up to 50 m.p.h.swept across the Southland on Monday, whipping up fires that scorched more than a dozen homes from Ventura to Los Angeles and Riverside counties and forced evacuation of 50 homes and a school.

Four homes were destroyed and two were damaged in Diamond Bar in a midafternoon blaze that started in brush at the base of a slope and burned uphill to homes with wood-shake roofs and worth about $350,000 each, Los Angeles County Fire officials said.

No injuries were reported.

George Azpeitia, 42, said he first noticed the fire about 3 p.m. as it quickly spread from his next-door neighbor’s house to his home in the 1700 block of Redgate Circle. Azpeitia said he tried unsuccessfully to fight the flames with a garden house.

“It’s devastated,” he said, hugging his wife, Blanca, as they stood outside their heavily damaged home. “But it’s not the end of the world.”

High winds quickly spread fire that erupted in a garage at the rear of a 150-unit townhouse complex in San Dimas to the wood-shake roofs of three homes, which Los Angeles County firefighters could not save.

County Fire Inspector John Lenihan said the blaze “very well could have been a repeat of the Sept. 15 West Covina fire,” in which 70 units in an apartment complex were destroyed in a wind-whipped fire.

In addition to the residences in the 12500 block of Meadowglen Lane, two cars in the garage were destroyed, officials said.

Residents of the homes escaped without injury. An evacuation center was set up at San Dimas High School.

The cause of the fire, which was reported about 4:30 p.m., was under investigation.

In Riverside, at least 15 homes in the Anza Narrows area near the Santa Ana River sustained minor damage to their roofs and back yards, and at least 50 homes and a junior high school had to be evacuated.

Riverside City Fire Capt. Richard Ballinger said the blaze started around 10 a.m. and by evening had blackened at least 125 acres in the area, much of which is covered by heavy brush. Although danger to homes in the area decreased as the day wore on, the fire still posed a problem for firefighters as it headed into overgrown vegetation.

In San Bernardino County, fire raced through about 50 acres of brush-covered land along the Cajon Canyon foothills, briefly threatening the Tree House Fun Ranch nudist colony.

By late afternoon, the blaze was headed toward Glen Helen Regional Park, said Greg Cooper, spokesman for the California Department of Forestry and Fire Protection. No structures were burned or threatened.

The fire broke out about 2:10 p.m. and was being fanned by strong winds. About 150 firefighters were battling the blaze.

“They are mainly trying to get a line around it and get the forward progress stopped,” Cooper said. “The problem is the winds. It’s pretty windy out here. That’s adding to the problem.”

The cause was under investigation.

Another fire in San Bernardino County forced the evacuation of about 100 people in Duncan Canyon north of Fontana, authorities said. Winds reaching 30 m.p.h fanned the fire across a grass-covered field. A shed was destroyed.

Winds gusting to 40 m.p.h. knocked down power lines and brought warnings of increased fire danger in Ventura County. Fire officials reported one small brush fire, but they expected a severe risk to continue today and Wednesday.

The Diamond Bar fire, which burned about 20 acres, started in heavy brush on a slope and was driven to the homes by winds that gusted to 30 m.p.h., fire officials said.

“It was moving pretty quick,” county fire Capt. Bob Grafton said. “Dry winds were pushing it.”

The four houses that were destroyed were on Redgate Circle and Shade Hill Drive. All were two stories high and had wood-shingle roofs.

Sheriff’s Sgt. Gilbert Aguilar said a resident reported her children hearing a “pop--not an explosion” and then saw the fire marching up the slope.

Several roads in the area were blocked off as about 280 county firefighters, using water-dropping helicopters and bulldozers, worked to contain the flames. The fire was reported under control at 5 p.m., about an hour and a half after it was first spotted.

Gary Newmann, a meteorologist for the National Weather Service, said he expects the winds, generated by a high-pressure area over the Western United States, to persist through the rest of the week.

Authorities issued a red-flag fire alert for mountain and hillside areas because of the combination of heat, wind and low humidity.

The temperature peaked at 93 degrees and the relative humidity fell to as low as 13% at the Los Angeles Civic Center on Monday.

Forecasters said Southland highs should range from the upper 80s to the upper 90s today.

Times staff writers Russell Ben-Ali, Greg Braxton, Irene Chang, Henry Chu, Darrell Dawsey, Nieson Himmel and Tracy Wilkinson contributed to this article.