Natural hot spring · Idaho
Sunflower Flat Hot Spring
Custer County, Idaho · 42 miles west of Challis, ID
Last updated
- Type
- Natural Natural hot spring
- Water temperature
- 109°F (43°C) at the source
- Cost
- Not recorded
- Hours or season
- Not recorded
- Clothing
- Not recorded
- Nearest town
- Challis, ID (42 mi / 67 km)
- Coordinates
- Pools or sources
- 1
- Historical record only: this spring has not been confirmed on the ground since 1981 and may be on private land.
About Sunflower Flat Hot Spring
Sunflower Flat Hot Spring is a natural hot spring in Custer County, Idaho, about 42 miles west of Challis, ID. The nearest large city is Boise, ID, roughly 97 miles away as the crow flies.
The temperature at the source has been recorded at 109°F (43°C). That puts it in the "very hot" range. Hotter than a hot tub. Enter slowly, keep soaks short and get out if you feel dizzy.
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
Very hot. Hotter than a hot tub. Enter slowly, keep soaks short and get out if you feel dizzy.
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 Sunflower Flat Hot Spring. Other colored dots are nearby springs in this directory. Coordinates: 44.73300, -115.01800.
Getting there
- Nearest town: Challis, ID. The spring is about 42 miles (67 km) west of town in a straight line.
- Nearest large city: Boise, ID, about 97 miles (156 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 Sunflower Flat Hot Spring
- Sunflower Hot Springs 149°F
- Indian Creek Hot Spring 190°F
- Middle Fork Indian Creek Hot Spring 162°F
- Cox Hot Springs 131°F
- Pistol Creek Hot Springs 115°F
- Loon Creek Hot Spring 120°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 Sunflower Flat Hot Spring?
The temperature at the source has been recorded at 109°F (43°C), which is very hot. Hotter than a hot tub. Enter slowly, keep soaks short and get out if you feel dizzy.
Where is Sunflower Flat Hot Spring?
Sunflower Flat Hot Spring is in Custer County, Idaho, about 42 miles west of Challis, ID. The GPS coordinates are 44.7330, -115.0180.
Can you soak at Sunflower Flat Hot Spring?
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 Sunflower Flat Hot Spring?
The closest listed spring is Sunflower Hot Springs, about 1.2 mile east. Indian Creek Hot Spring is about 7.1 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.