Santa Ana Winds Lash the Region : Weather: The hot desert air brings warmer temperatures to the coast and unusually clear skies to Simi Valley and Thousand Oaks.

Santa Ana winds gusting to 40 m.p.h. swept across Ventura County on Monday, knocking down power lines, tripping burglar alarms, aggravating allergies and raising concern about brush fires.

The hot desert winds also brought unusually clear skies to Simi Valley and Thousand Oaks by pushing pollution out to sea. In reverse of the usual pattern, Ventura was smoggier than Simi Valley on Monday, air quality officials said. The same is expected today.

In another reverse of the norm, Ventura, with a high of 89 degrees, was hotter than Simi Valley, where the high was 82 on Monday. Even higher temperatures are predicted for today, with highs in the low 90s in Ventura and Oxnard, the mid-90s in Ojai and the upper 80s in Simi Valley.

Only one minor brush fire was reported Monday in Ventura County, a two-acre blaze along the Simi Valley Freeway that caused no property damage. But officials said the risk of brush fires will continue today and Wednesday as the Santa Ana winds persist.

The state fire marshal’s office has issued a “red flag warning” through Wednesday for all of Southern California because of the extreme fire danger.

Fires scorched more than a dozen residences in Southern California and forced evacuation of 50 residences and a school. No injuries were reported.

Four residences were destroyed and two were damaged in Diamond Bar in Los Angeles County in a blaze that started in brush and burned uphill to houses worth about $350,000 each, Los Angeles County fire officials said.

High winds also spread a 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 residences, which Los Angeles County firefighters could not save.

In Riverside, at least 15 residences near the Santa Ana River received minor damage and at least 50 residences and a junior high school had to be evacuated.

In Ventura County, the Fire Department has called in off-duty firefighters to staff its four water-tender trucks, which provide water in remote locations.

“We’ve been sitting and waiting for the big one,” said Sam Meier, a department spokeswoman. “So far, nothing.”

But Southern California Edison crews were busy Monday.

“We are having several wind-related problems,” said Mark Olson, Edison area manager for Ventura County.

In Camarillo, the strong gusts blew down power distribution lines on Hobart Drive at 10:48 a.m., Olson said, cutting power to 3,670 customers. All but a few had power restored within 30 minutes, he said.

The wind also played havoc with home-security systems as it rattled windows and doors, triggering dozens of false alarms. Sheriff’s Lt. Kelli McIlvain said more than 80 false alarms were recorded in the Thousand Oaks and Moorpark areas, compared with 20 to 30 on a normal day. Winds began picking up about 1 a.m. Monday, according to Meier of the Fire Department. By 3:30 a.m. temperatures had risen 20 degrees and humidity had plummeted from about 60% to 10%, she said. The strong winds were expected to continue today and Wednesday, said Steve Burback, a meteorologist for WeatherData Inc., which provides forecasts for The Times.

Santa Ana winds occur when air pressure is higher inland than it is over the ocean. The inland high pressure--centered over southwest Idaho on Monday--is pushing hot desert air to low-pressure areas over the Pacific, raising temperatures, sucking up moisture and stirring up dust and pollen.

Dr. Lewis Kanter said the winds stir up local particulates and bring in sagebrush and tumbleweed pollen from the desert. “I’ve got a lady in the office who was perfectly fine until yesterday, when her asthma kicked in, apparently for no reason--the no reason being Santa Ana winds.”

Kanter said most cases can be treated with cortisone, antihistamines and other anti-inflammatory drugs, although some asthma sufferers require hospitalization. He advised anyone with a respiratory problem to try to stay indoors with air-conditioning turned to the recirculate setting.

Air-pollution levels in the county were well within the moderate range, but the normal pattern was reversed, said Philip Moyal, of the Ventura County Air Pollution Control District.

Ventura measured 52 on the district’s pollution index Monday while Simi Valley, which usually has the county’s highest pollution readings, came in at 38. Moyal predicted even higher levels for Ventura today.

Friday, Simi Valley measured 56 and Ventura’s reading was 33, Moyal said.

Burback said the winds are pushing pollution more than 100 miles out to sea, which makes it less likely that the smog will drift back over the coastal areas when onshore breezes return, probably by the end of the week.

Another victim of Santa Ana winds is agriculture, Ventura County’s biggest industry.

“No question about it, when Santa Anas come, it dries things up more than normal,” said Lawrence Yee, county director of the UC Cooperative Extension Service.

James Barker, whose family farms about 800 acres and runs a vegetable stand in Somis, said the dry winds burned the tops of his carrots, beets and radishes.

“Nobody wants to buy a bunch of radishes with the tops shriveled and dehydrated,” Barker said.

No wind-related traffic accidents were reported Monday, but the California Highway Patrol issued wind advisories until further notice for all of the county’s highways. Jan Carr, a dispatcher supervisor at the CHP’s Ventura office, said drivers of campers, trailers and other high-profile vehicles are advised to be especially careful.