The firefighter's death on Thursday in the San Bernardino National Forest east of Los Angeles raised the death toll to at least 35 in the catastrophic spate of wildfires raging across the western United States in recent weeks.

Twenty-six of those victims have died in California, including two other firefighters - a Forest Service contractor killed in a lightning-sparked fire in northern California, and a private helicopter pilot whose chopper crashed on a water-dropping mission in Fresno County last month.

Authorities withheld the identity of the latest firefighter fatality pending notification of next of kin.

That blaze has since charred more than 8500 hectares and was 66 per cent contained as of Friday, authorities said. Twelve firefighters have suffered minor injuries and at least 10 structures have been destroyed by that fire.

Scores of wildfires have blackened some 1.3 million hectares in California since mid-August and another 650,000 hectares in Oregon and Washington state since Labor Day, September 7.

The blazes, described by scientists and officials as unprecedented in scope and magnitude, have largely incinerated several small towns and destroyed thousands of dwellings in all three states. The fires, many sparked by intense lightning storms, were stoked early on by record-breaking heat, drought-parched vegetation and bouts of howling winds.

Civilians account for the remaining 23 confirmed fire-related deaths in California since mid-August, as well as the eight in Oregon and one in Washington state. Thousands of evacuees, particularly in Oregon, remained huddled in emergency shelters, mobile trailers and hotel rooms.

Communities in Oregon, unaccustomed to wildfires of such magnitude and lacking sufficient resources to deal with them, was especially hard hit.

Emergency management officials have warned the death toll there could climb as search teams scour the ruins of homes engulfed in flames during chaotic evacuations early in the disaster.

Thundershowers brought drenching rains to the western slopes of the Cascade Mountains late Thursday and through Friday, helping a force of more than 6000 firefighters make further headway against 10 major blazes still burning in Oregon.

The heavy rains also prompted flood and landslide warnings in areas where fire has stripped hillsides and canyons of vegetation.

A key sign of success in the three states' efforts to control the fires has been a steady rise in containment, a measure of the buffer lines that firefighters carve around the perimeter of each blaze by hacking away unburned vegetation to prevent its spread.

Australian Associated Press