Thomas Creek Ranch Hot Spring delivers 138°F water on state-managed land in Custer County, requiring a short walk of roughly 244 meters from the road. With a pH of 9.3 and sodium-dominant chemistry at 86 mg/L, the water emerges from a deep-circulation geothermal system at 4,400 feet elevation on Idaho Department of Lands property.
The spring occupies a mid-elevation valley in central Idaho's rugged backcountry near Challis, where sagebrush benchlands transition into forested mountain slopes. The Middle Fork of the Salmon River drainage dominates the broader landscape. Annual snowfall reaches 98 inches, and average air temperature sits at 44.8°F, producing cold winters and short summers. The terrain around Thomas Creek is characteristic of Idaho's basin-and-range country — open rangeland cut by creek drainages flanked by steep ridgelines.
History of Thomas Creek Ranch Hot Spring
The ranch in the name points to historical homesteading along Thomas Creek, though specific ownership records are not widely documented. The spring sits on a State Recreation Management Area under Idaho Department of Lands, indicating the state has formally recognized the site's recreational value. Custer County's hot springs were known to Indigenous peoples and later to ranchers and miners who settled the Salmon River country in the 1860s and 1870s.
Access is best from late June through September, as winter snow and cold limit travel in this part of Custer County. The walk from the road is short but may cross uneven terrain. Water at 138°F is dangerously hot — do not enter without testing and mixing with cooler water. Boundary Creek Campground, about 31 km away, provides reservable sites near the Middle Fork Salmon River launch point.
Is Thomas Creek Ranch Hot Spring worth visiting?
Best for
- Hot spring soaking
- Overnight camping trips
Thomas Creek Ranch Hot Spring is well suited for hot spring soaking and overnight camping trips.
Annual Precip: 22.0 in
Annual Snow: 98.3 in
December
Air 23°F · Water 138°F · +115° contrast
January
Air 26°F · Water 138°F · +112° contrast
February
Air 28°F · Water 138°F · +110° contrast
December offers 48°F more contrast than July
Recent Temperature
143.6°F
(62.0°C)
Measured Jun 27, 1980
The water at Thomas Creek Ranch Hot Spring is alkaline (pH 9.3).
pH influences mineral absorption through skin
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
Overview
Boundary Creek Campground is located at the edge of the Frank Church River of No Return Wilderness, adjacent to the boat launch for the Middle Fork of the Salmon River in Idaho. The site generally provides overnight camping for boaters waiting to launch the next day on their permit to float the Middle Fork.
Of the 15 campsites, 5 can be reserved during the high-use season (June 15-Aug. 15); the remaining 10 are first-come, first-served. Outside of those dates, all 15 sites are first-...
Reserve on Recreation.gov →
Swimsuit & towel
Water bottle
Stay hydrated, especially in hot water
Warm layers
Cold air before and after soaking
Camping gear
Nearby camping at Boundary Creek Campground
Trash bag
Pack out what you pack in
Water shoes
Hot ground near source
33 miles from Challis, ID
USGS Quad: GREYHOUND RIDGE 15 · NOAA: 10.0 · AMS Map: CHALLIS
What is the water temperature at Thomas Creek Ranch Hot Spring?
Thomas Creek Ranch Hot Spring has a water temperature of 138°F (59°C). This is considered a hot spring, well above body temperature.
Where is Thomas Creek Ranch Hot Spring located?
Thomas Creek Ranch Hot Spring is located in Custer County, Idaho at 4,400 feet elevation, near Challis. Coordinates: 44.7210°N, 115.0100°W.
How do I get to Thomas Creek Ranch Hot Spring?
Thomas Creek Ranch Hot Spring has Short Walk road access (0.2 mi from the road).
Is Thomas Creek Ranch Hot Spring free to visit?
Thomas Creek Ranch Hot Spring has Open access. It is managed by SDOL.
Can I camp near Thomas Creek Ranch Hot Spring?
Yes, Boundary Creek Campground is located nearby (19.1 miles away).
What minerals are in the water at Thomas Creek Ranch Hot Spring?
Water chemistry analysis shows the presence of pH, Calcium, Magnesium, Sodium, Sulfate, Chloride. The pH is 9.3 (alkaline).
Is it safe to soak at Thomas Creek Ranch Hot Spring?
At 138°F, Thomas Creek Ranch 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 Thomas Creek Ranch Hot Spring crowded?
Thomas Creek Ranch Hot Spring sees varying levels of visitors depending on the season and day of the week.
What should I bring to Thomas Creek Ranch Hot Spring?
Essentials for Thomas Creek Ranch Hot Spring: swimsuit, towel, water bottle, warm layers for before and after soaking, 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.