Upper Loon Creek Hot Springs
By the HotSpringsFind editorial team · How we compile records · Reviewed September 2026
Upper Loon Creek Hot Springs is a primitive hot spring listed near Challis, Idaho. Reported soak temperature: 104°F. See the visit fact sheet.
Current status
Four rock-walled soaking pools along Loon Creek inside the Frank Church-River of No Return Wilderness (Salmon-Challis NF) — a ~7-8 mile hike up Loon Creek Trail from the trailhead near the Upper Loon airstrip, with 145F-class sources and one large waterfall-fed pool; reachable only July-October when the rough access road is open.
Checked March 2026 · based on recent visitor reports · 4 sources ↓
Before you go
- Status: Open — last verified below — confirm via USFS Salmon-Challis NF — Loon Creek Area MF2 (roads single-track, snow-closed in winter; wilderness rules).
- Cost: Reported free access — fees and permits can change, confirm before visiting.
- Getting there: No verified hike distance on record — confirm the route and road conditions.
- Water: Reported soak temperature 104°F — always test the water before entering.
- Rules: Reported clothing-optional; reported dog-friendly.
- Conditions: check weather, fire closures, and land-manager alerts the week you go — mountain access changes seasonally.
- Reservations/permits: No permit required for wilderness hiking/camping (self-registration may apply); Salmon-Challis NF Middle Fork Ranger District manages — check trail conditions with the district.
- Best time to go: July-September (road open, trail snow-free); early October if road still passable. Completely snowbound otherwise.
- Clothing reality: No rules (wilderness); suits optional customarily; remote.
- Kids: Allowed.
- Cell service: none — download maps and tell someone your plan.
- Accessibility: Wilderness backpacking only; no facilities.
- ACCESS WINDOW ~JULY-OCTOBER: Loon Creek Road (NF-007) and Beaver-Loon Road (NF-172) are single-track dirt with high passes closed by snow all winter; Indian Springs Rd (NF-004) is steep/narrow/unmaintained
- ~7-8 miles north of Loon Creek airstrip/trailhead up Loon Creek Trail — backpacking trip, not a day soak for most
- Four sources in sequence along the trail: #1 small 2-person pool, #2 ~4-person pool (a bit hot, bucket provided), #3 the prize — a 10-15-person pool fed by a hot waterfall, #4 stagnant algae pools (skip)
- USGS-measured source ~65C/149F — scalding at origin; pools are creek-tempered, test first
- Frank Church-RONR Wilderness rules: no motorized/mechanized travel, group-size limits, Leave No Trace; good primitive campsites right by pools #2 and #3
- Owen Cabin Hot Spring is just beyond pool #4 — same trail, weaker soaking (see its record)
- Upper Loon backcountry airstrip and Tin Cup Campground near the trailhead; ~27+ miles of dirt road from the ID-75/Yankee Fork area — nearest real services Challis or Stanley
- Wildlife: rattlesnakes, black bears, moose; bear-scat reported
- Hazard: 145F-class source water at vents
- Hazard: Rattlesnakes reported at the springs
- Hazard: Bears (food storage required)
- Hazard: Rough seasonal dirt-road approach with high passes
- Hazard: Remote — no services, no cell
About this spring
A complex of four separate hot spring sources spaced along the Loon Creek Trail in the Frank Church-River of No Return Wilderness — rock-walled sand-bottom pools including a 4-person pool and a large 10-15 person pool fed by a hot waterfall. Source up to ~145°F; a bucket is typically on site for mixing cold creek water. Access road open only ~July-October. Remote wilderness — bears, rattlesnakes. Source water scalding. No facilities.
Upper Loon Creek Hot Springs is a complex of four separate thermal sources spaced along the Loon Creek Trail in the Frank Church-River of No Return Wilderness, roughly 7-8 miles north of the Loon Creek backcountry airstrip near Tin Cup Campground. The pools are rock-walled with sand, gravel, and rock bottoms: the first is a small two-seater, the second a medium four-person soak (a bucket is typically on site for adding creek water), the third — nicknamed Crescent Moon — is the showpiece, a 10-15-person pool fed by a hot waterfall beside a campsite and a collapsing old cabin, and the fourth holds two stagnant, algae-laden pools unsuitable for soaking.
A USGS field measurement in July 1979 recorded the source at 149°F (65°C) with strongly alkaline, sodium-dominant water (pH 9.3). The Loon Creek trailhead access road is open only about July through October, and Owen Cabin Hot Springs lies farther up the trail. Wildlife sign — bears, moose, mountain lion, snakes — is abundant in the drainage.
Directions & trailhead access
~25-31 mi of rough dirt roads (FR 172/FR 007) from Hwy 75 near Sunbeam to Tin Cup Campground at the wilderness boundary, then hike ~5.5 mi up the Loon Creek Trail with creek fords.
Idaho geothermal context
Idaho's thermal water rides the old track of the Yellowstone hotspot across the Snake River Plain and surfaces along faults in the surrounding mountains. Many of the best soaks are roadside or river-access pools inside national forests — including springs that only emerge when river levels drop. Backcountry sites demand real navigation skills and long dirt-road drives.
What a primitive site means here
Primitive springs have no facilities: no changing rooms, no trash service, often no maintained road to the pool. Expect natural rock or gravel bottoms, water temperature that varies by spot and season, and other visitors who may treat the site informally. Pack out everything you bring, test the water before entering, and leave the pool cleaner than you found it.
Best time to visit
Year-Round (Best: May – October)Pool temperatures and access can change with weather and season. Outdoor ambient temperatures fluctuate significantly across Idaho. Late spring through autumn offers the most comfortable road access.
Fact sheet
| Reported soak temp | 104°F |
|---|---|
| Source temp (historical) | 149°F |
| Trail access | Recorded coordinates — access unverified |
| Access fee | Reported free — verify locally |
| Clothing policy | Reported clothing-optional |
| Pet policy | Reported dog-friendly |
| Geothermal data reference | NOAA Thermal Springs List (1980 archive) |
| Check land status | USFS Salmon-Challis NF — Loon Creek Area MF2 (roads single-track, snow-closed in winter; wilderness rules) |
Upper Loon Creek Hot Springs FAQ
Is Upper Loon Creek Hot Springs open right now?
Four rock-walled soaking pools along Loon Creek inside the Frank Church-River of No Return Wilderness (Salmon-Challis NF) — a ~7-8 mile hike up Loon Creek Trail from the trailhead near the Upper Loon airstrip, with 145F-class sources and one large waterfall-fed pool; reachable only July-October when the rough access road is open. (Status based on recent visitor reports, last checked March 2026.)
Is Upper Loon Creek Hot Springs free?
Upper Loon Creek Hot Springs is listed as free to access in Custer County, Idaho. Fees and rules change — verify current status with the land manager before visiting.
What temperature is Upper Loon Creek Hot Springs?
Upper Loon Creek Hot Springs has a reported soak temperature of 104°F and a historical source temperature of 149°F in survey records. Historical data may not reflect current conditions — always test water before entering.
Is Upper Loon Creek Hot Springs clothing optional?
Upper Loon Creek Hot Springs is listed as traditionally clothing-optional in directory records. Confirm current rules before visiting, as policies change.
How do you access Upper Loon Creek Hot Springs?
Upper Loon Creek Hot Springs is on public land — verify current road access, fees and rules with the land manager before visiting.
Sources & references
- USFS Salmon-Challis NF — Loon Creek Area MF2 (roads single-track, snow-closed in winter; wilderness rules) — official · 2026
- IdahoHotSprings.com — Upper Loon Hot Springs 1-4 (pool-by-pool report, rated A) — community · 2003-07
- AllTrails — Loon Creek Trail (11.5 mi, wilderness, dogs leashed) — community · 2025
- SoakingSprings.com entry (directory lead; USGS 65C confirmation) — community · 2026-03
Details above were verified against the named sources on their listed dates — conditions change, so recheck before traveling. · How we verify our data · Report a correction
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