Wind has wreaked havoc with wildfires threatening two crown jewels of the US National Park Service, pushing the flames towards man-made and natural attractions in and around Glacier and Yosemite national parks.
The wind-driven fires, combined with high temperatures and dry conditions, have disrupted holiday travel and hampered firefighters across the West during a Labour Day weekend that capped a devastating summer in which an area larger than Rhode Island has burned.
The dozens of fires burning across the West and Canada have blanketed the air with choking smoke from Oregon, where ash fell on the town of Cascade Lakes, to Colorado, where health officials issued an air quality advisory alert.
A fire in Montana's Glacier National Park emptied the park's busiest tourist spot as wind gusts drove the blaze towards the doorstep of a century-old lodge.
The 14-square-mile fire that consumed a historic Glacier backcountry chalet last week was about a mile away from Lake McDonald Lodge, a 103-year-old Swiss chalet-style hotel.
The lodge's setting on the lake as the Going-to-the-Sun-Road begins its vertigo-inducing climb up the Continental Divide has made it an endearing park symbol for many visitors, and it is the starting point for hikes, boat rides, horseback riding and bus tours.
Rangers evacuated tourists and residents from 55 homes near the lake on Sunday as firefighters laid hoses and sprinklers around the hotel. On Monday, fire crews got bad news: the wind had shifted and gusts were driving the fire down the mountainside toward the lake's shores.
Losing Lake McDonald Lodge on top of the destruction of Sperry Chalet last week would be "unimaginably devastating", said Mark Hufstetler, a historian who worked at the lodge for several years in the late 1970s and early 1980s.
"These are some of the most remarkable buildings anywhere in the United States and they are an integral part of the Glacier experience and the Glacier tradition," Mr Hufstetler said. "If they did not exist, that experience and that tradition would not exist either."
Fire crews understood the significance of the lodge and were ready to protect it, said fire information officer Diane Sine.
"It's important to all of us and a very high priority to do whatever we can to preserve that," she said.
Outside California's Yosemite National Park, a wind-fuelled fire on Sunday drove deeper into a grove of 2,700-year-old giant sequoia trees, but officials were not sure whether trees had been killed.
Giant sequoias are resilient and can withstand low intensity fires, said fire information officer Anne Grandy.
"We don't know the intensity of the fire," she said. "It could be your standard fire that the grove has experienced for thousands of years."
There are more than 100 giant sequoias in the grove, including the 24-storey-high Bull Buck sequoia, one of the world's largest.
The fire was one of several in the area, one of which closed some trails in Yosemite. A road leading to the park's southern entrance was also closed.
Elsewhere in northern California, a fire destroyed 72 homes and forced the evacuation of about 2,000 people from their houses. The fire has burned 14 square miles in the community of Helena, about 150 miles south of the Oregon border.
In Los Angeles, a fire that destroyed four homes and threatened hillside neighbourhoods is no longer actively burning, but firefighters remained at the scene in case the wind reignited the blaze, Fire Department Chief Ralph Terrazas said.