Wildfires in California and Montana have exploded in size amid windy, hot conditions and have quickly encroached on neighbourhoods, forcing evacuation orders for more than 100 homes, while an Idaho blaze is spreading.
In California's Klamath National Forest, the fast-moving McKinney fire, which started on Friday, went from charring about one square kilometre to scorching as much as 160 sq km by Saturday in a largely rural area near the Oregon state line, according to fire officials.
"It's continuing to grow with erratic winds and thunderstorms in the area and we're in triple-digit temperatures," US Forest Service spokeswoman Caroline Quintanilla said.
California Governor Gavin Newsom declared a state of emergency on Saturday as the fire intensified.
In Montana, the Elmo wildfire nearly tripled in size to about 28 sq km within a few miles of the town of Elmo.
About 320km to the south, Idaho residents remained under evacuation orders as the Moose fire in the Salmon-Challis National Forest charred 175 sq km in timbered land near the town of Salmon.
It was 17 per cent contained.
Meanwhile, crews made significant progress in battling another major blaze in California that forced evacuations of thousands of people near Yosemite National Park earlier this month.
The Oak fire was 52 per cent contained by Saturday, according to a Cal Fire incident update.
As fires raged across the West, the US House on Friday approved wide-ranging legislation aimed at helping communities in the region cope with increasingly severe wildfires and drought - fuelled by climate change - that have caused billions of dollars in damage to homes and businesses in recent years.
The bill now goes to the Senate.