Natural hot spring · Idaho
Foster Ranch Hot Springs
Lemhi County, Idaho · 23 miles northwest of Challis, ID
Last updated
- Type
- Natural Natural hot spring
- Water temperature
- 135°F (57°C) at the source
- Cost
- Not recorded
- Hours or season
- Not recorded
- Clothing
- Not recorded
- Nearest town
- Challis, ID (23 mi / 37 km)
- Coordinates
- Pools or sources
- 1
- Scalding: recorded at 50°C or above. Water at this temperature causes burns in seconds.
- Historical record only: this spring has not been confirmed on the ground since 1981 and may be on private land.
About Foster Ranch Hot Springs
Foster Ranch Hot Springs is a natural hot spring in Lemhi County, Idaho, about 23 miles northwest of Challis, ID. The nearest large city is Boise, ID, roughly 106 miles away as the crow flies.
The temperature at the source has been recorded at 135°F (57°C). That puts it in the "too hot to enter at the source" range. Water this hot can burn skin quickly. Soaking pools are usually cooled by mixing with creek or tap water. Never enter the source itself.
It is a natural spring with little or no development. Some natural springs have rock pools you can sit in, while others are too hot, too shallow or on land where soaking is not allowed.
This spring comes from the US federal Thermal Springs List compiled in 1981. Nobody has confirmed it on the ground for this directory since, so treat the details as historical. Many springs on that list sit on private ranch land, so never visit without permission.
Water temperature
Too hot to enter at the source. Water this hot can burn skin quickly. Soaking pools are usually cooled by mixing with creek or tap water. Never enter the source itself.
Readings come from the NOAA thermal springs list, and other public sources. Temperatures change with season, flow and pool design. See our soak temperature guide for safe soaking times.
Map and directions
Red marks Foster Ranch Hot Springs. Other colored dots are nearby springs in this directory. Coordinates: 44.66100, -114.65200.
Getting there
- Nearest town: Challis, ID. The spring is about 23 miles (37 km) northwest of town in a straight line.
- Nearest large city: Boise, ID, about 106 miles (171 km) in a straight line.
- Use the directions buttons above for a driving route. Final roads to many springs are unpaved, seasonal or closed in winter, so check road conditions before you go.
Weather forecast
Live forecast for this exact spot from the US National Weather Service.
Hot springs near Foster Ranch Hot Springs
- Shower Bath Springs 122°F
- Owen Cabin Hot Spring 133°F
- Upper Loon Creek Hot Springs 145°F
- Loon Creek Hot Spring 120°F
- Cox Hot Springs 131°F
- Hospital Hot Spring 115°F
Before you go
- Check the operator, land manager or park website for current hours, fees and closures. Details in any directory can go out of date.
- Pack out everything you bring, including food scraps. Do not use soap in natural pools.
- Keep your head above water. Warm fresh water can carry Naegleria fowleri, a rare but deadly amoeba that enters through the nose.
- Drink water, limit soaks to 10 to 20 minutes at a time in very hot water, and skip alcohol.
- Read our hot spring etiquette guide and safety guide.
Frequently asked questions
How hot is Foster Ranch Hot Springs?
The temperature at the source has been recorded at 135°F (57°C), which is too hot to enter at the source. Water this hot can burn skin quickly. Soaking pools are usually cooled by mixing with creek or tap water. Never enter the source itself.
Where is Foster Ranch Hot Springs?
Foster Ranch Hot Springs is in Lemhi County, Idaho, about 23 miles northwest of Challis, ID. The GPS coordinates are 44.6610, -114.6520.
Can you soak at Foster Ranch Hot Springs?
The source is too hot to enter safely. Natural springs vary. Some have pools built by visitors, others are too hot or shallow, and some are on private land or in areas where bathing is banned. Check local rules and test the water before you get in.
What hot springs are near Foster Ranch Hot Springs?
The closest listed spring is Shower Bath Springs, about 3.4 miles southeast. Owen Cabin Hot Spring is about 4.2 miles away.
What should I bring to a hot spring?
Water to drink, a towel, sandals with grip, a bag to pack out trash, and warm layers for after your soak. At primitive springs bring a headlamp and tell someone where you are going.
Sources and corrections
This listing combines the NOAA NCEI Thermal Springs List. Data last refreshed August 2026. Source 1
Visited recently? Send a correction, such as a temperature reading, fee, closure or photo. If you look after this spring and want it removed, see removal requests.