A haze has sat in the Gallatin Valley since Tuesday, the color of weak tea, drifting down from the Panther Creek and Wapiti fires across the border. By Wednesday the Bridgers were a suggestion rather than a range. At the Sourdough trailhead the air quality index read 147, which is technically unhealthy for sensitive groups but mostly just means your throat feels like you swallowed a wool sock.

Mara Lindquist, 34, of Belgrade, was tapping her inhaler against her palm at the kiosk. “I drove up from Three Forks for this,” she said. “The app said moderate at 6 a.m. By the time I parked it was orange. I’m going anyway. My knees need the elevation.”

RangerDistrict 3 posted a notice at the trailhead printed on neon orange cardstock. It advised reducing exertion, staying hydrated, and considering lower-elevation alternatives. Someone had added in ballpoint pen: “or just breathe less.” The note remained unsigned.

On the trail the light was flat and gold. Aspen leaves showed silver undersides in the still air. A party of four MSU students passed going up, two wearing N95s, two wearing nothing, all carrying Coldsmoke packs. Coming down, a man in a cotton T-shirt coughed into his elbow and said the view from the saddle was “worth the lung tax.”

At the saddle the smoke lay thick in the Madison Valley. The Tobacco Roots were gone. The Gravellys were gone. You could see the next ridge and that was it. A red-tailed hawk circled below eye level, unbothered. Lindquist ate a peanut butter wrap on a lichen-covered boulder and checked her watch. “Forty minutes up,” she said. “Forty down. Be home for the kids’ dinner.”

The parking lot was full when she returned. A Subaru with a “Native” bumper sticker waited for her spot, engine idling, AC running.