Sunflower Hot Springs
Drag the handle to compare the two views. The orange dot marks the spring, in a frame about three quarters of a mile wide.
Sunflower Hot Springs comes out scalding, near 150 degrees, on Boise National Forest land in Custer County around 40 miles from Challis. Wikipedia calls it a geothermal mineral spring. The approach is half a mile of walking and access is marked open. The source water is far too hot to enter.
The spring sits at roughly 4,400 feet in country that sees snowfall short of a hundred inches and modest precipitation, averaging mid forties across the year. It is half a mile in from the road, and no one has written down which road. Forest Service land with a plain National Forest designation and no fee mentioned.
December to February is the listed window. Boundary Creek Campground is twenty miles away. The 1980 USGS sample found alkaline water. At nearly 150 degrees the water will burn skin on contact; only a pool that has cooled well below that is safe, and the record says nothing about one existing.
Wikipedia's short entry places Sunflower Hot Springs within Boise National Forest and calls the water geothermal and mineral. OpenStreetMap and the USGS both carry the same name.
Aircraft with laser scanners measured this ground to within inches. The scan strips out trees and buildings, leaving the bare shape of the land around Sunflower Hot Springs.
- Setting
- Hillside
- The spring sits on a steep slope that climbs to the northwest.
- Highest ground nearby
- 586 ft above the spring
- Within a quarter mile, to the northwest
A slice through the ground from northwest to southeast, about 0.6 miles end to end.
Elevation data: USGS 3D Elevation Program. Aerial imagery: USGS The National Map. Public domain.
That's about twice the US average of 65. It's higher than at 71% of the springs on this site.
Heat flow measures the warmth working its way up through the ground from deep inside the earth. Where it runs high, rain and snowmelt that seep down through cracks in the rock come back up hot.
See every spring on the geothermal heat map →
Heat flow estimate: Stanford Thermal Earth Model (Aljubran & Horne, 2024), CC BY 4.0.
The water at Sunflower Hot Springs is alkaline (pH 9.3).
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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-...
Sunflower Hot Springs is road-accessible, so you can bring more gear. The water is dangerously hot, so bring water shoes and test pools carefully.
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