Cape Horn Warm Springs
Cape Horn Warm Springs sits at 6,555 feet in Boise County, one of the higher thermal features near Idaho City, producing 95-degree Fahrenheit water with an exceptionally alkaline pH of 9.6. Reaching it requires a walk of about 3,460 feet from Beaver Creek Road through terrain that receives nearly 15 feet of snow annually, keeping this spring quiet and seldom visited.
The approach crosses high mountain meadow and scattered timber at an elevation where the air is thin and cool, averaging just 38 degrees year-round. The spring emerges in a clearing where the warm water sustains a patch of green growth even as surrounding vegetation goes dormant in fall. Views stretch across the Capehorn meadows, a broad alpine opening where moose and elk are regularly spotted at dawn. The water feels warm rather than hot, comfortable for extended soaking. In winter, deep snow buries the access route and isolates the spring entirely.
The walk from Beaver Creek Road covers about two-thirds of a mile over uneven ground with no formal trail. Thatcher Campground is 2 miles away with five first-come, first-served sites, vault toilets, and drinking water. At 95 degrees, the water is comfortable for soaking without needing to mix with cold water. Snow closes access from roughly November through June at this elevation. Bring a GPS device or detailed map, as the spring is not signed.
The spring's extreme alkalinity and low calcium at 1.4 mg/L reflect classic Idaho Batholith geothermal chemistry, where water circulates deep through granite before emerging at the surface. The 82 mg/L sodium concentration and 39 mg/L sulfate are moderate. Nearby Thatcher Campground, just off Highway 21, overlooks the same Capehorn meadows and has served as a base camp for exploring this high country since the Forest Service developed the area decades ago.
The water at Cape Horn Warm Springs is alkaline (pH 9.6).
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This campground is just off Highway 21, and tucked back into the trees, overlooking beautiful Capehorn meadows. Walk across the street to overlook a marshy wetland, a hangout for breakfasting moose, elk, and a variety of birds. Each of the 5 sites is equipped with picnic tables and fire rings with cooking grills. The campground accommodates trailers and motorhomes up to 32 feet and has vault toilets and hand pumps for drinking water. Although there are no full hookups, the campground will fit...
Cape Horn Warm Springs sits at 6,555 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 26% stronger than at sea level, so bring sunscreen and drink more water than you normally would.
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Cape Horn Warm Springs is road-accessible, so you can bring more gear. Cold air temperatures make a changing robe or warm layers essential.
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