Straight Creek Hot Spring
Straight Creek Hot Spring runs at 144 degrees Fahrenheit right alongside Middle Fork Road in the Boise National Forest, emerging 97.8 degrees above ambient air temperature. With a pH of 9.6, this is among the most alkaline thermal features in Idaho, indicating deep circulation through the granitic Idaho Batholith.
Just 68 feet from the road at 4,100 feet elevation in Boise County, the spring sends steam into the forest canopy along the Middle Fork of the Boise River corridor. The extremely low mineral content, with only 1.6 mg/L calcium and 1.8 mg/L chloride, produces water that feels almost unnaturally soft. Annual snowfall exceeds 10 feet, and the average air temperature holds at 46.2 degrees, creating substantial thermal contrast at the spring. USGS measurements confirmed 65 degrees Celsius, consistent with deep geothermal circulation.
The Middle Fork Road corridor follows a fault zone through the Boise National Forest where multiple thermal features emerge. Straight Creek's exceptionally high pH and minimal mineral content indicate water that has spent extended time in contact with granitic rock at depth, dissolving silica while leaving behind heavier minerals. The Boise National Forest holds one of the highest concentrations of accessible hot springs in the American West, a product of the shallow heat source beneath central Idaho.
The spring sits right off Middle Fork Road near Idaho City, but the 144-degree source temperature causes severe burns. Do not enter the water at the source. Look downstream for areas where hot water has cooled or mixed with creek water. Barber Flat Cabin, a rentable 1935 CCC-built guard station, sits about five miles away for overnight stays. The road is typically passable from late May through October in a standard vehicle.
Is Straight Creek Hot Spring worth visiting?
Best for
- Observing powerful hot springs
- Easy day trips
- Overnight camping trips
Not ideal for
- Casual soaking
The water at Straight Creek Hot Spring is alkaline (pH 9.6).
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Overview The Barber Flat Cabin site was established for administrative use by the Forest Service in 1923, and was used prior to that by the Barber Lumber Company. At the time, the Forest Service used a cabin already on-site as a guard station and then built a new one in 1927. The current cabin and outbuildings were built by the Civilian Conservation Corps in 1935, and the cabin today looks much as it did back then. Guests can drive to Barber Flat Cabin in two-wheel drive passenger cars or tr...