Stanley Hot Spring
Stanley Hot Spring sits just 66 feet from the Salmon River Scenic Byway at 6,220 feet elevation, making it one of the easiest thermal features to reach in Idaho's Challis National Forest. The 106-degree water provides a comfortable soaking temperature without needing to mix in cold water.
Pulling off the scenic byway, the spring is essentially at the roadside in the heart of Custer County. The Salmon River runs nearby through a forested valley that collects over 12 feet of snow each winter. At 39.6 degrees average annual air temperature, this is cold country, and the spring's 66.4-degree thermal surplus above ambient makes the warm water feel especially inviting. Alkaline water with a pH of 8.8 has a slippery, soft quality that distinguishes it from the river water just steps away.
The spring draws from the same deep geothermal system that heats dozens of features across the Sawtooth and Salmon River region. Water chemistry shows low mineralization with just 60 mg/L sodium and 31 mg/L sulfate, indicating rapid circulation through clean granite rather than prolonged contact with sedimentary rock. The Challis National Forest encompasses some of Idaho's most thermally active terrain, a consequence of the shallow magmatic intrusions beneath the region.
Park along the Salmon River Scenic Byway and walk less than a minute to the spring. The 106-degree temperature is comfortable for direct soaking. Sunny Gulch Campground, about 3.5 miles away along the Salmon River, accepts reservations and provides a convenient base. The scenic byway itself offers outstanding driving between Stanley and Challis. The spring is accessible whenever the highway is clear, typically May through November.
Is Stanley Hot Spring worth visiting?
Best for
- Hot spring soaking
- Easy day trips
- Overnight camping trips
- Winter soaking with dramatic temperature contrast
The water at Stanley Hot Spring is alkaline (pH 8.8).
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Overview Sunny Gulch Campground sits along the shores of Salmon River in the forests of central Idaho. Recreation Excellent fishing is right out your back door on the Salmon River, with rainbow trout, Westslope cutthroat trout and occasional hybrid cutbows and bull trout available. Sunny Gulch lies in the heart of the Sawtooth National Recreation Area. A myriad of excellent hiking and biking opportunities are available, and an estimated 750 miles of trails crisscross the valley and surround...