When a wall of flames raced up the hillside at Avalanche Creek on a recent afternoon, firefighters in Yosemite National Park had to act quickly.

The giant Ferguson Fire was headed toward the south rim of Yosemite Valley, and if crews didn’t stop it here, the fire would open up on the edge of the park’s most beloved spot. Already, 10,000 acres of Yosemite had been charred, and much of the park was entering its third week of closure.

But just as the blaze began spitting hot embers out of the creek drainage and across Glacier Point Road, where helicopters with water buckets and engine teams with chain saws had staked their line of defense, firefighters caught a break — at least for the moment.