Robinson Bar Hot Springs
Robinson Bar Hot Springs reaches 131 degrees Fahrenheit at 5,960 feet along National Forest Development Road 454 in Custer County. The water runs 90 degrees above the ambient air temperature, one of the largest thermal differentials among Idaho's roadside springs, with a TDS of 294 mg/L and iron content of 80 micrograms per liter.
The Yankee Fork of the Salmon River defines this landscape, a narrow, forested valley flanked by steep mountains in the heart of the Sawtooth Range. The spring surfaces just 230 feet from the gravel road, its outflow staining nearby rocks with iron deposits. Lodgepole pine and spruce dominate the surrounding forest. Winters are long and cold here, with over 10 feet of annual snowfall and average temperatures hovering around 41 degrees.
The spring is roadside via NF Road 454, though the road itself is remote and seasonal. Pole Flat Campground sits about 4.5 miles away with vault toilets, drinking water, and sites accommodating trailers up to 32 feet. The source water is dangerously hot and must cool before any contact. Access roads typically close from late fall through early summer depending on snowpack.
Robinson Bar takes its name from a historic river crossing and ranch site along the Yankee Fork, a drainage famous for 1870s gold dredging. The spring's chemistry, with 74 mg/L sodium, 50 mg/L sulfate, and 15 mg/L chloride, reflects deep circulation through the batholith before the water surfaces. Trace iron at 80 micrograms per liter accounts for the orange and rust-colored mineral staining visible near the source.
The water at Robinson Bar Hot Springs is alkaline (pH 9.4) with 294 mg/L total dissolved solids.
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This campground is away from the main road and up the hill overlooking the river and the dredge ponds. Campsites include picnic tables tent pads fire rings with cooking grills. Campground amenities include a vault toilet and drinking water. Sites accommodate trailers and motorhomes up to 32 feet long.
Robinson Bar Hot Springs sits at 5,960 feet above sea level, way above the mile-high mark. You may not feel the altitude strongly, but hot water still dehydrates you faster at elevation. UV is about 24% stronger than at sea level, so bring sunscreen and drink more water than you normally would.
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Robinson Bar Hot Springs is road-accessible, so you can bring more gear. The water runs hot, so extra hydration is key. Cold air temperatures make a changing robe or warm layers essential.
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