Firefighters Gain on Sierra Blazes : Nature: Lessening winds and cooler temperatures aid crews. More than 30 buildings have been destroyed.

Cooler temperatures and diminishing winds allowed firefighters Monday to get the upper hand on two Sierra foothill blazes that have destroyed more than 30 homes and other buildings and charred about 1,300 acres of wild lands.

State fire officials Monday said a 500-acre fire near the town of Rough and Ready, 60 miles east of Sacramento, was triggered when a power line fell on an oak tree.

A blaze that consumed more than 800 acres near the town of Kelsey--about 10 miles northeast of Placerville--was determined late Monday to have been the work of an arsonist. Fire officials released no further details.

No serious injuries were reported in either fire.

Karen Terrill, a California Division of Forestry spokeswoman, said the blazes, along with a third major fire along the California-Nevada state line, contributed to an extremely busy weekend for firefighters.

“Our resources were stretched very tight,” she said, adding that state authorities still managed enough resources to fight the fires.

What has fire officials fretting is that communities in the tinder-dry Sierra Nevada foothills are just entering the heart of the state’s annual fire season.

“We’re having a very busy fire season and the worst is yet to come,” Terrill said, noting that the fire risk will increase as the late summer heat makes the state’s forests and brushlands even drier and seasonal north winds pick up.

Even before the potentially worst part of the fire season, she said, 4,525 blazes have been reported statewide to forestry officials this year--a more than 25% jump from the same period of 1993. Officials cite as causes the growing population in rural communities as well as drought and other weather conditions.

Scott Cunningham, a Sacramento-based meteorologist with the National Weather Service, agreed about the potential fire risk. “It looks like a more active fire season . . . in general throughout the western United States,” he said, explaining that a number of fires have been touched off during thunder and lightning storms.

Cunningham said that temperatures in the Sierra foothills Monday dropped seven to nine degrees and that wind gusts began to diminish. “As soon as we get rid of these winds tomorrow we’ll be in better shape,” he said.

In the largest of the weekend blazes, 1,200 firefighters remained on the lines Monday battling the Kelsey fire in steep terrain. Twelve structures were reported destroyed, including five homes.

Authorities said the fire was about 70% contained and they expected to have it totally contained by tonight. The fire began Sunday afternoon.

About 40 miles north of the Kelsey fire, a power line fell on an oak tree, igniting flames Sunday afternoon that eventually consumed about 500 acres near Rough and Ready.

Airplanes flying as low as 150 feet dropped fire retardant chemicals to stop flames from spreading in the fast-growing foothill area.

The fire, which destroyed six homes and more than a dozen other buildings, forced hundreds of residents to flee, some to homes of friends and others to evacuation centers. Authorities began allowing them to return Monday.

The third fire, called the Crystal Peak blaze and located at the California-Nevada border, was fully contained about 6 p.m. Monday. Since the fire began Thursday, it has consumed 7,310 acres and destroyed three homes and several other buildings.

On Monday, about 300 firefighters remained on the fire lines near the Nevada town of Verdi, about 10 miles from Reno. The blaze was caused by heavy machinery used to clear an area to plant trees, said Sharon Brockman, a fire information officer with the U.S. Forest Service.

Winds on the fire lines picked up late Monday afternoon, but a fire official said, “So far . . . the line is holding.”

Another blaze south of Reno had consumed 5,000 acres by Monday evening. Officials reported that an outbuilding and a trailer were burned in the fire at Holbrook Junction on U.S. 395, 15 miles south of Gardnerville near the state line.