Thousands of evacuees displaced by deadly wildfires in Oregon settled into a second week of life in shelters and car camping as fire crews battled on against the blazes, and search teams scoured the ruins of demolished homes for those still missing.

With state resources stretched to their limit, Oregon Governor Kate Brown has requested a federal disaster declaration from the White House to bolster US government assistance for emergency response and relief efforts.

Dozens of fires have charred some 4.5 million acres (1.8 million hectares) of tinder-dry brush, grass and woodlands in Oregon, California and Washington state since August, ravaging several small towns, destroying thousands of homes and killing at least 34 people.

Eight deaths have been confirmed during the past week in Oregon, which became the latest and most concentrated hot spot in a larger summer outbreak of fires across the entire western United States. The Pacific Northwest was hardest hit.

The conflagrations, which officials and scientists have described as unprecedented in scope and ferocity, have also filled the region's skies with smoke and soot, compounding a public health crisis already posed by the coronavirus pandemic.

Satellite images showed high-altitude plumes of smoke from the fires drifting as far east as New York City and Washington, D.C., carried aloft by the jet stream.

The fires roared to life in California in mid-August, and erupted across Oregon and Washington around Labor Day last week, many of them sparked by catastrophic lightning storms and stoked by record-breaking heat waves and bouts of howling winds.

Weather conditions improved early this week, enabling firefighters to begin to make headway in efforts to contain and tamp down the blazes.

The California Department of Forestry and Fire Protection (CalFire) said 16,600 firefighters were still battling 25 major fires on Tuesday, after achieving full containment around the perimeter of other large blazes.