Heat Eases, but Fires Still Burn : Weather: Rising humidity makes it seem hotter, forecasters say. High temperatures are expected to return for the holiday weekend.

The enduring heat wave eased only temporarily Monday, and firefighters continued their battle against four wildfires that had scorched more than 12,000 acres of brush and timberland, destroying 10 homes, incinerating about 50 vehicles and injuring at least eight people.

Although Monday’s high temperatures generally were 5 to 10 degrees below the marks that shattered some Southland records Sunday, it was still plenty hot, with top readings of well over 100 in many Los Angeles-area communities.

Rising humidity made it seem even hotter, and the National Weather Service issued a special “excessive heat” advisory warning that “a potentially dangerous combination of heat and humidity is developing in the valleys . . . of Southern California.”

While temperatures topped out at 105 in the San Fernando and San Gabriel valleys on Monday, humid air pumped in from a tropical storm system over Baja California made it seem 5 to 10 degrees hotter, the weather service said.

The moist air triggered some strong thunderstorms over the San Bernardino Mountains and the western Mojave Desert on Monday afternoon. Residents of Victorville, Apple Valley and Barstow were warned of possible flash floods.

Curtis Brack, a meteorologist with WeatherData Inc., said that while the humidity will drop a little as the week progresses, the temperatures will start rising again, with hot weather expected through the extended Fourth of July weekend.

Noting that people working outside for extended periods will be susceptible to sunstroke, heat cramps and heat exhaustion, the weather service advisory suggested drinking lots of water and reducing activity levels whenever possible.

The most destructive of the fires--a 2,820-acre blaze northwest of the San Gabriel Mountain community of Wrightwood--was 95% contained Monday night after burning 10 houses and dozens of trucks and cars, said Jaquie Stiver, a U.S. Forest Service spokeswoman.

Stiver said four of the more than 1,300 firefighters brought in from across the Southwest suffered minor injuries. The blaze was started by a campfire near a Boy Scout camp, but Stiver stressed that Scouts were not responsible.

Breezes in the Wrightwood area were light Monday, and the slow spread of the fire permitted the release of water-dropping planes to other blazes still raging out of control.

Twenty miles to the west, near Soledad Pass, a brush fire in Kentucky Springs Canyon was about half contained after charring more than 3,500 acres of chaparral. Stiver said four more firefighters sustained minor injuries fighting that blaze, which was started by a tracer bullet deflected from a target at a rifle range.

Almost 1,000 firefighters were battling the Soledad fire at nightfall Monday.

In Riverside County, more than 500 firefighters were struggling to control a blaze that had consumed about 1,500 acres of dense brush in the Anza area by Monday afternoon. The going was hot and slow, and with the fire only 40% contained by midafternoon, officials said it probably would be sometime late today before the fire is fully contained.

In the Cleveland National Forest, a 4,200-acre fire roared out of control Monday afternoon, chewing its way rapidly through heavy brush a few miles east of the San Diego County community of Ramona. A fire official said the 330 firefighters on the lines had managed to contain only about 10% of the blaze. He made no predictions when the fire would be controlled.

For firefighters, the forecast was not good. Temperatures are expected to rise a couple of degrees a day through Wednesday, and while dropping humidity will make the heat a little more bearable, the drier air will increase the fire hazard.

The high temperature at Los Angeles Civic Center was 94 degrees Monday, seven degrees below Sunday’s top mark of 101. Monday’s overnight low was 73, tying the record for the warmest minimum on a June 27, set in 1990. The relative humidity ranged between 29% and 75%.

Other high temperatures Monday included 106 in Woodland Hills, 105 in Pasadena, 102 in Monrovia, 96 in San Gabriel, 95 in El Toro, 88 in Torrance, 83 at Los Angeles International Airport and 74 in Newport Beach.

Brack said the continuing heat is the product of an immense dome of high pressure--centered over Arizona--that is refusing to budge. He said that as long as the dome stays in place, it will block the onshore flow of cool breezes from the ocean.

“Right now, it looks like not much change through the weekend,” he said. “It’s gonna stay hot.”