Bridge Hot Springs

Bridge Hot Springs — also known as Elk Flats — takes its name from its setting: user-built pools on both sides of the South Fork Boise River, beneath the bridge just before Featherville, Idaho. A popular campground within walking distance supplies most of the soakers, and late summer is both the busiest and the best time: the pools submerge during spring runoff and can run too cool early in the season, so the dependable soaks come once the river drops.

Baumgartner Hot Springs

Baumgartner Hot Springs is the Featherville area’s developed soak: a commercial-style concrete pool inside Baumgartner Campground on the South Fork Boise River, about 11 miles east of Featherville in the Sawtooth National Forest. The 101°F water is piped into a 15×20-foot concrete pool with steps, a railing, and filters — and it is drained, cleaned, and refilled every morning during the season. Usage is extreme and families pack it; the standing local advice is simple: soak early.

Round the Bend Hot Spring

Round the Bend Hot Spring is exactly what the name says: the steaming cliff face just around the bend from Ninemeyer on the Middle Fork Boise River. It is also, honestly, not a soak in the usual sense — there is no pool here at all. Hot water streaked with bright algae flows down a cliff straight into the river, and the only way to enjoy it is to wade in during late summer, when the river drops to about 3 feet deep, and find the seam where hot meets cold.

Smith’s Cabin Hot Springs

Smith’s Cabin Hot Springs is a trio of undeveloped hot springs — numbered 1, 2, and 3 — strung along both sides of the Middle Fork Boise River near Troutdale Campground in the Atlanta corridor. All three are filed under “potential”: the first sits on the road side of the river, the second across the river slightly upstream, and the third about 100 yards further up, originating roughly 20 yards above the river. On documented visits, soaking pools were marginal or absent entirely — this is a stop for spring hunters already working the corridor, not a destination soak.

Sheep Creek Bridge Hot Springs

Sheep Creek Bridge Hot Springs is a small, shallow set of rock-walled, tarp-dammed pools a short hike from one of the points where the Middle Fork Road bridges the Boise River, in the Atlanta corridor. It comes with an honest caveat: this spring has declined. The well-built pool documented in early visits was later dismantled, and the most recent accounts describe small silt- and mud-filled pools running lukewarm — a shadow of the soak it once was, though the source still flows and the setting, with river views, remains.

Phifer Warm Spring

Phifer Warm Spring — also known as Weatherby Mill — is one of the Atlanta area’s oddities: an 86°F warm spring with no soaking pool at all. Instead, the water is piped into a stand-up shower stall and an old bathtub, making this a rinse-off stop rather than a soak — best enjoyed on a hot summer day, when the lukewarm water is a feature instead of a bug.

Pete Creek Hot Springs

Pete Creek Hot Springs is built around a sight worth the trip by itself: a hot waterfall pouring into the Middle Fork Boise River in the Atlanta area. The soak — small, user-built rock pools below the falls on the far side of the river — exists only seasonally, roughly August through October when the river runs low. On documented visits outside that window there were no pools at all, just the falls and a cold river crossing, so time this one carefully.

Ninemeyer Hot Springs

Ninemeyer Hot Springs is a late-season-only proposition on the far side of the Middle Fork Boise River: rocky, user-built pools with sand and rock bottoms that sit submerged or unreachable for most of the year. The access window is small — fording the river is only advised at low water, usually late July through November — and on multiple documented visits the pools were only ever seen steaming from the wrong side of a swollen river.

Loftus Hot Springs

Loftus Hot Springs is a pair of user-built rock pools along the Middle Fork Boise River Road — famous, heavily used, and with a rough recent history: the pools were destroyed by vandals in 2011 and rebuilt by local soak seekers, in reduced form, later that year. The upper pool (102°F, mortar-reinforced) and lower pool (100°F) sit right off the washboard road between Boise and Atlanta, and usage here is extreme — this is a known party spot for hunters and ATVers, kegs and all. Two cautions from the listing itself: watch for broken glass in the pools, and poison ivy grows around them.

Granite Creek Hot Springs

Granite Creek Hot Springs is a seasonal riverside soak right next to the Middle Fork Road in the Atlanta area — a set of rock-walled pools with sand, gravel, and rock bottoms at the edge of the Middle Fork Boise River. Finding the right spot can be tricky: there may or may not be a pool ready depending on when you visit, and the pools that exist swirl hot and cold water together, so a good soak takes a little work.