Grandjean Hot Spring
Grandjean Hot Spring sits at 5,000 feet in the Boise National Forest, just 60 feet from the road in some of the most dramatic high-country terrain in central Idaho. Historical records classify it simply as hot without specifying a temperature, but the source has served soakers for well over a century along the route to the Sawtooth Wilderness.
The road to Grandjean follows a winding route east of Lowman through old-growth forest and granite outcrops. The spring emerges near the confluence of mountain drainages, where the air smells of wet earth and warming pine. This area receives over 15 feet of snow annually, the highest snowfall of any roadside-accessible hot spring in the Boise National Forest. Summer reveals wildflower meadows and clear creek channels running with snowmelt.
Roadside access makes reaching the spring straightforward, but the drive to Grandjean is long and partly on unpaved road. Highway 21 is seasonal and can close in heavy snow. With nearly 185 inches of annual snowfall, winter access is unreliable. Bonneville Campground offers reservable sites about 12 miles away and its own hot springs access.
The spring occupies a geologically active zone at the edge of the Idaho Batholith, where granitic intrusions fractured the crust and created pathways for heated water. Its proximity to the Sawtooth Wilderness boundary places it in terrain shaped by Pleistocene glaciation. The Bonneville Campground, about 12 miles away, highlights the area's long soaking tradition with its own nearby hot springs.
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Overview Bonneville Campground is 19 miles east of Lowman, Idaho just off Highway 21 at an elevation of 4,700 feet. Warm Springs Creek runs alongside the campground and the South Fork Payette River lies across the highway. Visitors enjoy soaking at Bonneville Hot Springs a short distance above the campground, and fishing in the creek and river.Recreation A 1/4-mile hiking trail leads from the campground to Bonneville Hot Springs, where a soaking pool awaits. Warm Springs Creek offers good tro...
Grandjean Hot Spring is road-accessible, so you can bring more gear. Cold air temperatures make a changing robe or warm layers essential.
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