Elkhorn Hot Spring

Custer County, Idaho · Near Challis
44.2450°N, 114.8850°W · 6,155 ft
136°F 24°F air · Good soaking weather 6,155 ft Open Roadside SDOL Camping nearby (4.9 mi)
Aerial view of the ground around Elkhorn Hot Spring LiDAR bare-earth view of the same ground around Elkhorn Hot Spring
Aerial LiDAR bare earth

Drag the handle to compare the two views. The orange dot marks the spring, in a frame about three quarters of a mile wide.

Elkhorn Hot Spring, also known as Boat Box Hot Spring, is a Custer County roadside spring on the Salmon River Scenic Byway. The tub water comes in hot, mid 130s. Open access. The land is Idaho Department of Lands ground under an SRMA designation. Challis is the nearest town on file at 37 miles, though the Wikipedia entry places the spring about three miles from Stanley. For camping, the record points to Sunny Gulch Campground.

Location

The byway passes within about 240 feet. Elevation is high and the yearly mean hovers around 40. A dozen feet of snow is a normal winter here. The spring itself is the tub Wikipedia describes, on the riverbank, so the setting is the Salmon River and the highway beside it.

December through February are the listed best months. A highway corridor under twelve feet of snow usually gets plowed, but find out. The water needs cooling in the tub before you get in. No chemistry is on file. Sunny Gulch is the closest camping.

History of Elkhorn Hot Spring

Wikipedia calls this Boat Box Hot Spring and says it is also known as Elkhorn Hot Spring. The spring is a single metal tub fed through a plastic tube built into the Salmon River bank, about three miles from Stanley on Idaho State Highway 75. The name comes from a historical wooden tub that was used before annual spring flooding destroyed it.

Terrain

Aircraft with laser scanners measured this ground to within inches. The scan strips out trees and buildings, leaving the bare shape of the land around Elkhorn Hot Spring.

Setting
Canyon floor
Steep ground climbs away on both sides of the spring.
Highest ground nearby
455 ft above the spring
Within a quarter mile, to the southeast
Cross-section through the spring

A slice through the ground from northwest to southeast, about 0.6 miles end to end.

Elevation data: USGS 3D Elevation Program. Aerial imagery: USGS The National Map. Public domain.

Heat Below
132 milliwatts per square meter of heat flow

That's about twice the US average of 65. It's higher than at 82% of the springs on this site.

Heat flow measures the warmth working its way up through the ground from deep inside the earth. Where it runs high, rain and snowmelt that seep down through cracks in the rock come back up hot.

Heat flow estimate: Stanford Thermal Earth Model (Aljubran & Horne, 2024), CC BY 4.0.

Monthly Climate
22°
Jan
24°
Feb
30°
Mar
35°
Apr
43°
May
54°
Jun
65°
Jul
64°
Aug
54°
Sep
40°
Oct
27°
Nov
19°
Dec
Annual Precip: 27.3 in Annual Snow: 146.4 in
Best Time to Visit
December Air 19°F · Water 136°F · +117° contrast
January Air 22°F · Water 136°F · +114° contrast
February Air 24°F · Water 136°F · +112° contrast
December offers 46°F more contrast than July
Current Conditions
24°F
S 12.1 mph 91% Good soaking weather
Today 69° Low 30° Sunny
Spring is +67° warmer
Wednesday 74° Low 35° Sunny 6% precip
Spring is +62° warmer
Thursday 68° Low 33° Chance Light Rain then Showers And Thunderstorms 82% precip
Spring is +68° warmer
Friday 67° Low 31° Chance Light Rain 36% precip
Spring is +69° warmer
Saturday 70° Low 32° Sunny 9% precip
Spring is +66° warmer
Where to Stay

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Nearby Camping
Sunny Gulch Campground 4.9 mi away

Overview Sunny Gulch Campground sits along the shores of Salmon River in the forests of central Idaho. Recreation Excellent fishing is right out your back door on the Salmon River, with rainbow trout, Westslope cutthroat trout and occasional hybrid cutbows and bull trout available. Sunny Gulch lies in the heart of the Sawtooth National Recreation Area. A myriad of excellent hiking and biking opportunities are available, and an estimated 750 miles of trails crisscross the valley and surround...

Reservable Yes
Reserve on Recreation.gov →
Mile-High Advisory 6,155 ft

Elkhorn Hot Spring sits at 6,155 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 25% stronger than at sea level, so bring sunscreen and drink more water than you normally would.

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Temperature
136°F
Warm Hot Boiling
Water Temp 136°F (58°C)
Avg Air Temp 40°F
Above Ambient +96°F
Great soaking conditions September
Access
Open
Road Access Roadside
Nearest Road Salmon River Scenic Byway
Distance to Road 239 ft
Land
Ownership State
Agency SDOL
Designation SRMA
Unit Idaho Department of Lands
Manager SDOL
Protection 3 - Protected, subject to extractive use
Frequently Asked Questions
What is the water temperature at Elkhorn Hot Spring?
Elkhorn Hot Spring has a water temperature of 136°F (58°C). This is considered a hot spring, well above body temperature.
Where is Elkhorn Hot Spring located?
Elkhorn Hot Spring is located in Custer County, Idaho at 6,155 feet elevation, near Challis. Coordinates: 44.2450°N, 114.8850°W.
How do I get to Elkhorn Hot Spring?
Elkhorn Hot Spring has Roadside road access, with the nearest road being Salmon River Scenic Byway (239 ft from the road).
Is Elkhorn Hot Spring free to visit?
Elkhorn Hot Spring has Open access. It is managed by SDOL.
Can I camp near Elkhorn Hot Spring?
Yes, Sunny Gulch Campground is located nearby (4.9 miles away).
Is it safe to soak at Elkhorn Hot Spring?
With care. At 136°F Elkhorn Hot Spring is hot enough to need short sessions, fifteen to twenty minutes, and plenty of water. Enter slowly and get out if you feel light-headed.
Sources: USGS NWIS, Wikipedia