Entry No. 57 — the Boise file — filed under: soak
Bonneville Hot Springs
A quarter-mile walk along Warm Springs Creek through the Boise National Forest leads to user-built rock pools and a rustic soak shack with a cast-iron tub fed by piped thermal water. It's far enough off Highway 21 that traffic noise disappears, leaving just the creek and, after dark, a thick scatter of stars overhead. The springs stay open year-round even when the adjacent campground gates close, making it a genuine wild soak rather than a developed resort.
The story
Seventy-five miles out of Boise along mountain Highway 21, past Lowman, Warm Springs Creek cuts through the Boise National Forest. Here, geothermal water bubbling up to 180 degrees Fahrenheit seeps out of the granite hillside, trickling down mineral-stained rock into user-built stone pools along the riverbank. But you didn't drive into the backcountry just for another muddy river soak—you came for the off-grid bathhouse sitting on a small bluff just above the steam.
Perched among the Ponderosa pines sits a rustic wooden soak shack, built directly over the thermal runoff. Inside, there are no locker rooms or attendant desks—just a single, weathered cast-iron clawfoot bathtub hooked up to a plastic pipe that continuously channels raw, unchlorinated hot spring water straight from the mountain. You plug the drain with a carved wooden stopper, let the scalding mineral water fill the iron basin, and take a private bath isolated in the middle of a national forest.
Because the Forest Service manages this as an undeveloped day-use site rather than a paved commercial resort, there are no neon signs, gift shops, or concrete turnstiles. You park in the campground lot, drop five dollars cash into the self-service envelope, and hike back along the creek path where highway noise completely disappears into the rush of cold mountain water.
What it's like
Arrive after sunset on a weeknight when the weekend crowd thins out. Pay the $5 day-use fee at the trailhead envelope box, flip on a headlamp, and follow the quarter-mile dirt path along Warm Springs Creek as the pine air turns heavy with sulfur. You'll spot steam rising against the conifers, signaling the riverside rock pools below and the soak shack above. If someone is already inside the shack, wait your turn in the lower rock pools where hot runoff mixes with icy creek water. When the shack frees up, pull the wooden stopper to drain the previous soak, let fresh thermal water fill the tub, and sink in under an intense dark sky. Keep in mind that soap and nude soaking are strictly banned by Forest Service rules, and when the main campground gate closes for winter, you'll need to hike an extra half-mile each way past the snow gate.
The move: Time a clear-night arrival, hike in by headlamp, and sink into a creekside rock pool with the Milky Way directly above.
📍 Before you go Roughly 75+ miles from Boise on mountain Highway 21; soap and nude soaking are prohibited here, and winter access adds about a mile of hiking when the campground gate is closed.
- 📍 Lowman
- 💸 $
- ⚡ Low-key
- 🌗 Outdoors
Where: Forest Rd near Bonneville Campground, ~19 mi SE of Lowman off ID-21, Boise National Forest
Hours: Added 2026-06-24 — confirm current hours before you go.
Pair it with
- Boise State University Astronomical Observatory — Pair an urban rooftop stargazing session through BSU's 16-inch telescope with a midnight backcountry soak under real dark skies along Warm Springs Creek.
- Bruneau Dunes State Park Observatory — Combine central Idaho's best night-sky vantage points by following a high-desert session at a 25-inch observatory telescope with an off-grid bath in the forest.
- Crone's Cupboard — Pick up incense or ritual supplies at Boise's oldest occult shop before driving out for a late-night soak in a lone mountain shack.
Good to know
How much does it cost to soak at Bonneville Hot Springs?
Day use costs $5 per vehicle, payable via cash in the self-service fee envelope at the campground trailhead.
Are clothing-optional soaking and soap allowed?
No. Forest Service regulations strictly prohibit both nude soaking and the use of any soaps, shampoos, or detergents in the springs and creek.
How far is the hike from the parking lot?
It is a flat 0.25-mile walk along Warm Springs Creek when Bonneville Campground is open. When the campground gate is closed during winter, parking moves to Highway 21, adding about a half-mile to a mile to the hike.
How hot is the water in the tub and pools?
The geothermal source exiting the hillside reaches up to 180°F. Water inside the cast-iron tub typically settles around 104°F, while the riverside rock pools vary depending on how much cold creek water flows in.
Plan a visit & invite your people →
Further reading: fs.usda.gov · Official site · nomanbefore.com · alltrails.com · lorandjorexplore.com · Reddit
last checked: 2026-06-24