Salmon Hot Spring
Salmon Hot Spring surfaces at 113 degrees near the town of Salmon at 4,920 feet, distinguished by a near-neutral pH of 7.1 and unusually high sodium at 190 mg/L. That chemistry profile is rare among Idaho's thermal springs, most of which run strongly alkaline.
The spring emerges roadside in the Salmon River valley, just 100 feet from the access road in Lemhi County. The surrounding landscape is dry mountain terrain receiving about 19 inches of rain and five and a half feet of snow annually. The valley floor is wide here, framed by the Bitterroot and Lemhi ranges. The water has a faintly mineral taste and carries enough sodium to feel different from the river water nearby. Williams Lake Campground sits about 13 miles away in the surrounding national forest.
The neutral pH combined with high sodium, elevated chloride at 49 mg/L, and substantial calcium at 21 mg/L suggest this water follows a different geochemical path than most Idaho springs. Rather than the typical high-pH, calcium-stripped signature of granitic circulation, this chemistry points to contact with marine sedimentary rocks or evaporite deposits at depth. The Lemhi Valley sits in an active extensional basin where faulting provides pathways for deep water to rise.
The 113-degree water requires some cooling for comfortable soaking. The spring is roadside accessible near the town of Salmon, making it one of the easier thermal features to reach in Lemhi County. Williams Lake Campground, about 13 miles away, offers 11 first-come-first-served sites with lake access. The town of Salmon has full services including groceries, fuel, and restaurants.
Is Salmon Hot Spring worth visiting?
Best for
- Hot spring soaking
- Easy day trips
- Overnight camping trips
The water at Salmon Hot Spring is neutral (pH 7.1).
This campground has 11 sites near Williams Lake. Opportunities abound to hike or ride into the Salmon-Challis National Forest or to fish in the nearby lake or creek. The lake can be accessed at the Forest Service boat ramp and day-use area.