Cox Hot Springs

Custer County, Idaho · Near Challis
44.7850°N, 114.8550°W · 4,160 ft
131°F 32°F air · Good soaking weather 4,160 ft Open Hike US Forest Service Camping nearby (23.3 mi)

Backcountry, and a long way from anything: Cox Hot Springs sits in Custer County within the Boise National Forest per the record, 36 miles from Challis, and nothing closer counts as a town. Hot water, low 130s. The record marks access open. OpenStreetMap uses the same name. This is a hike-in spring with a photograph on file and nothing in the way of facilities.

Location

The walk is about two and three quarter miles from the closest road, one with no name on file. Elevation is middling for central Idaho. Snow comes in at close to eight feet a winter and the climate is otherwise moderate. Yellowjacket Guard Station is the closest listed camping, 23 miles away, so this is a long approach in both senses.

Winter gets the best-months tag, which for a near three mile hike through that much snow calls for snowshoes or waiting for the melt. Cooling is required before anyone sits in it. The chemistry was run in 1980 and came back alkaline. There is no developed camping anywhere near the spring; the guard station is the closest thing on file.

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 Cox Hot Springs.

Aerial view of the ground around Cox Hot Springs LiDAR bare-earth view of the same ground around Cox Hot Springs
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.

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

A slice through the ground from north to south, about 0.6 miles end to end.

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

Heat Below
120 milliwatts per square meter of heat flow

That's about twice the US average of 65. It's higher than at 71% 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
26°
Jan
29°
Feb
35°
Mar
42°
Apr
51°
May
60°
Jun
70°
Jul
70°
Aug
59°
Sep
43°
Oct
33°
Nov
23°
Dec
Annual Precip: 22.3 in Annual Snow: 92.7 in
Best Time to Visit
December Air 23°F · Water 131°F · +108° contrast
January Air 26°F · Water 131°F · +105° contrast
February Air 29°F · Water 131°F · +102° contrast
December offers 47°F more contrast than August
Current Conditions
32°F
Clear N 0.0 mph 93% Good soaking weather
Today 75° Low 46° Sunny
Spring is +56° warmer
Wednesday 80° Low 50° Sunny
Spring is +51° warmer
Thursday 75° Low 49° Rain Showers 81% precip
Spring is +56° warmer
Friday 73° Low 46° Chance Rain Showers 50% precip
Spring is +58° warmer
Saturday 76° Low 47° Sunny 10% precip
Spring is +55° warmer
Water Chemistry Sampled 1980-06-28

The water at Cox Hot Springs is alkaline (pH 8.9).

pH 8.9 Alkaline
pH influences mineral absorption through skin
Calcium 2 mg/L
May support bone density and joint health
Sodium 100 mg/L
Supports circulation and skin hydration
Sulfate 47 mg/L
Traditionally used for skin conditions and inflammation
Chloride 12 mg/L
Natural antiseptic with skin health benefits
Where to Stay

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Nearby Camping
Yellowjacket Guard Station 23.3 mi away

Overview Yellowjacket Guard Station is a historic Forest Service Ranger Station and Work Center. Originally constructed in 1925 and remodeled in 1934 by the Civilian Conservation Corps, the structure is eligible for listing on the National Register of Historic Places. Recreation Hikers, horseback riders, mountain bikers and off-road enthusiasts will find many trails in the surrounding area. Hunting is also a popular activity. Click here for an Idaho OHV safety messageFacilities The spacious...

Reservable Yes
Reserve on Recreation.gov →
Temperature
131°F
Warm Hot Boiling
Water Temp 131°F (55°C)
Avg Air Temp 45°F
Above Ambient +86°F
Great soaking conditions September
Access
Open
Road Access Hike
Distance to Road 2.7 mi
Land
Ownership Federal
Agency US Forest Service
Designation National Forest
Unit Boise National Forest
Manager US Forest Service
Protection 3 - Protected, subject to extractive use
Frequently Asked Questions
What is the water temperature at Cox Hot Springs?
Cox Hot Springs has a water temperature of 131°F (55°C). This is considered a hot spring, well above body temperature.
Where is Cox Hot Springs located?
Cox Hot Springs is located in Custer County, Idaho at 4,160 feet elevation, near Challis. Coordinates: 44.7850°N, 114.8550°W.
How do I get to Cox Hot Springs?
Cox Hot Springs has Hike road access (2.7 mi from the road).
Is Cox Hot Springs free to visit?
Cox Hot Springs has Open access. It is managed by US Forest Service.
Can I camp near Cox Hot Springs?
Yes, Yellowjacket Guard Station is located nearby (23.3 miles away).
What minerals are in the water at Cox Hot Springs?
Water chemistry analysis shows the presence of pH, Calcium, Sodium, Sulfate, Chloride. The pH is 8.9 (alkaline).
Is it safe to soak at Cox Hot Springs?
With care. At 131°F Cox Hot Springs 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.