Billy Hot Spring
Billy Hot Spring sits along the South Fork Salmon River corridor in the Payette National Forest, with recent USGS measurements recording water at 95 degrees Fahrenheit. The water chemistry skews strongly alkaline at pH 9.7, with elevated sodium and low calcium, typical of deep-circulating Idaho Batholith thermal water. A short walk of about three-quarters of a mile reaches the spring from the road.
At 5,790 feet elevation, the spring occupies a forested slope above the South Fork Salmon River in Valley County. Ponderosa pine and Douglas fir dominate the canopy, and the river canyon drops away steeply below. This area receives nearly 200 inches of snow annually, making winter access impractical. In summer, the warm water pools among rocks and roots, with the sound of the river audible from below. The setting feels genuinely remote despite the road's relative proximity.
The South Fork Salmon corridor follows a major fault system through the Idaho Batholith, and Billy Hot Spring is one of many thermal features along this trend. The water's high sodium content and low mineral load suggest deep circulation through granitic rock, where long contact time strips calcium and loads sodium into solution. The 95-degree surface temperature represents significant cooling during ascent from depths where temperatures likely exceed 300 degrees Fahrenheit.
The approach from South Fork Salmon River Road covers about 1.25 kilometers. Shoreline Campground at Warm Lake, 13 miles away, has reservable sites at 5,300 feet elevation with lake access. Summer is the practical window for visiting, roughly late June through September. Bring water and plan for no facilities at the spring.
Is Billy Hot Spring worth visiting?
Best for
- Overnight camping trips
The water at Billy Hot Spring is alkaline (pH 9.7).
Overview Shoreline Campground is located just across the road from beautiful Warm Lake, at an elevation of 5,300 feet. Visitors enjoy boating, fishing, swimming, hiking and viewing local wildlife. Recreation Warm Lake offers great fishing opportunities for cutthroat, rainbow, lake and bull trout. Boating, canoeing and swimming are popular activities. Billy Rice Swim Beach is nearby, offering a day-use site for picnicking and swimming. A boat ramp is located just across the road from the camp...