Hospital Hot Spring flows at 115°F deep in the Boise National Forest backcountry, requiring a genuine hike of over two miles from the nearest road. At 4,000 feet in Custer County near Challis, it rewards the effort with alkaline sodium-sulfate water carrying a total dissolved solids count of 278 mg/L and a pH of 8.9.
The trail to the spring crosses rugged terrain through mixed conifer forest in the Middle Fork country. The surrounding landscape is steep, rocky, and largely untracked, with few other visitors on most days. The Salmon River Mountains rise in every direction, and the drainage feels genuinely remote. Annual snowfall exceeds 100 inches, and the forest floor stays damp and mossy through early summer. The spring pools steam visibly in the cool mountain air.
History of Hospital Hot Spring
The name Hospital Hot Spring likely references early use by miners or settlers who believed in the therapeutic properties of mineral water. The chemistry bears this out with distinctive alkaline characteristics: zero detectable magnesium, very low calcium at 3.4 mg/L, and dominant sodium at 90 mg/L. The Boise National Forest manages the surrounding area, which falls within the broader Idaho Batholith where deep crustal fractures bring heated water to the surface.
Yellowjacket Guard Station, a historic 1925 structure remodeled by the CCC in 1934, is the nearest reservable accommodation at nearly 30 miles. The spring sits over 3,400 meters from the nearest road, so plan for a serious hike. Bring sufficient water and navigation tools. At 115°F, source water needs substantial cooling before contact. This is not a casual day trip; plan for backcountry conditions and variable weather.
Is Hospital Hot Spring worth visiting?
Best for
- Hot spring soaking
- Overnight camping trips
Hospital Hot Spring is well suited for hot spring soaking and overnight camping trips.
Annual Precip: 22.5 in
Annual Snow: 101.9 in
December
Air 25°F · Water 115°F · +91° contrast
January
Air 28°F · Water 115°F · +87° contrast
February
Air 30°F · Water 115°F · +86° contrast
December offers 49°F more contrast than July
Recent Temperature
114.8°F
(46.0°C)
Measured Jun 29, 1980
The water at Hospital Hot Spring is alkaline (pH 8.9) with 278 mg/L total dissolved solids.
pH influences mineral absorption through skin
Higher mineral concentration for therapeutic soaking
May support bone density and joint health
Known for muscle relaxation and stress relief
Supports circulation and skin hydration
Traditionally used for skin conditions and inflammation
Natural antiseptic with skin health benefits
Iron-rich springs may support circulation
Overview
Yellowjacket Guard Station is a historic Forest Service Ranger Station and Work Center. Originally constructed in 1925 and remodeled in 1934 by the Civilian Conservation Corps, the structure is eligible for listing on the National Register of Historic Places. Recreation
Hikers, horseback riders, mountain bikers and off-road enthusiasts will find many trails in the surrounding area. Hunting is also a popular activity. Click here for an Idaho OHV safety messageFacilities
The spacious...
Reserve on Recreation.gov →
Swimsuit & towel
Water bottle
Stay hydrated, especially in hot water
Camping gear
Nearby camping at Yellowjacket Guard Station
Trash bag
Pack out what you pack in
Water shoes
Hot ground near source
40 miles from Challis, ID
USGS Quad: RAMEY HILL 7.5 · NOAA: 3.0 · AMS Map: CHALLIS
What is the water temperature at Hospital Hot Spring?
Hospital Hot Spring has a water temperature of 115°F (46°C). This is considered a hot spring, well above body temperature.
Where is Hospital Hot Spring located?
Hospital Hot Spring is located in Custer County, Idaho at 4,000 feet elevation, near Challis. Coordinates: 44.8360°N, 114.7900°W.
How do I get to Hospital Hot Spring?
Hospital Hot Spring has Hike road access (2.1 mi from the road).
Is Hospital Hot Spring free to visit?
Hospital Hot Spring has Open access. It is managed by US Forest Service.
Can I camp near Hospital Hot Spring?
Yes, Yellowjacket Guard Station is located nearby (18.6 miles away).
What minerals are in the water at Hospital Hot Spring?
Water chemistry analysis shows the presence of pH, Total Dissolved Solids, Calcium, Magnesium, Sodium, Sulfate, Chloride, Iron. The pH is 8.9 (alkaline). Total dissolved solids measure 278 mg/L.
Is it safe to soak at Hospital Hot Spring?
At 115°F, Hospital Hot Spring is hot enough to require caution. Enter slowly, limit soaking sessions to 15–20 minutes, and stay hydrated. Always tell someone your plans before visiting remote hot springs.
Is Hospital Hot Spring crowded?
Hospital Hot Spring sees varying levels of visitors depending on the season and day of the week.
What should I bring to Hospital Hot Spring?
Essentials for Hospital Hot Spring: swimsuit, towel, water bottle, camping gear, a trash bag to pack out what you pack in. The water is over 110°F — test the temperature before entering and watch for scalding near the source.