Fire crews backed by water-dropping helicopters are struggling to suppress a huge wildfire that has displaced 2000 residents in southern Oregon, the largest among dozens of blazes raging across the drought-stricken western United States.
The Bootleg Fire has charred more than 91,860 hectares of desiccated timber and brush in and around the Fremont-Winema National Forest since erupting on July 6 about 400km south of Portland.
More than 1700 firefighters and a dozen helicopters were assigned to the blaze, with demand for personnel and equipment across the Pacific Northwest beginning to strain available resources, said Jim Gersbach, a spokesman for the Oregon Department of Forestry.
"It's uncommon for us to reach this level of demand on firefighting resources this early" in the season, he said.
No serious injuries have been linked to the Bootleg Fire, officials said, but it has destroyed at least 21 homes and 54 other structures, and forced an estimated 2000 people from several hundred dwellings placed under evacuation. Nearly 2000 homes were threatened.
Other states hard hit by the latest spate of wildfires include California, Idaho, Montana and Alaska.
As of Wednesday, the centre in Boise put its "national wildland fire preparedness level" at 5, the highest of its five-tier scale, meaning most US firefighting resources are currently deployed somewhere across the country.
The situation represents an unusually busy start to the annual fire season, coming amid extremely dry conditions and record-breaking heat that has baked much of the West in recent weeks.
Scientists have said the growing frequency and intensity of wildfires are largely attributable to prolonged drought that is symptomatic of climate change.