Granite Creek Hot Spring

Boise County, Idaho · Near Idaho City
43.8030°N, 115.4010°W · 4,205 ft
131°F 33°F air · Good soaking weather 4,205 ft Open Roadside US Forest Service Camping nearby (6.9 mi)

Granite Creek Hot Spring is Forest Service land in Boise County, part of the Boise National Forest, a 21 mile run from Idaho City off Middle Fork Road. Low 130s at the source, hot. Access is recorded as open. Barber Flat Cabin, about seven miles off, is the closest camping on record. An image is on record, though nothing on file describes how or whether the water is pooled.

Location

You can see the spring from the road; it is about 240 feet off Middle Fork Road at a little over four thousand feet. Winters drop around ten feet of snow; the climate is wet year round. That is the extent of what the record says about the site.

December into February is the window the best-months note favors. With ten feet of snow the drive becomes the variable, since the spring itself is roadside. The water needs cooling. A 1981 sample is the only chemistry on file and it read alkaline. Barber Flat Cabin is where the record points for camping.

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 Granite Creek Hot Spring.

Aerial view of the ground around Granite Creek Hot Spring LiDAR bare-earth view of the same ground around Granite Creek 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.

Setting
Canyon floor
Steep ground climbs away on both sides of the spring.
Highest ground nearby
464 ft above the spring
Within a quarter mile, to the north
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
123 milliwatts per square meter of heat flow

That's about twice the US average of 65. It's higher than at 74% 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
27°
Jan
29°
Feb
36°
Mar
41°
Apr
50°
May
61°
Jun
72°
Jul
71°
Aug
61°
Sep
46°
Oct
34°
Nov
25°
Dec
Annual Precip: 29.9 in Annual Snow: 121.1 in
Best Time to Visit
December Air 25°F · Water 131°F · +106° contrast
January Air 27°F · Water 131°F · +104° contrast
February Air 29°F · Water 131°F · +102° contrast
December offers 47°F more contrast than July
Current Conditions
33°F
NW 0.0 mph 98% Good soaking weather
Tuesday 74° Low 43° Sunny
Spring is +57° warmer
Wednesday 81° Low 49° Sunny
Spring is +50° warmer
Thursday 72° Low 54° Showers And Thunderstorms 77% precip
Spring is +59° warmer
Friday 72° Low 50° Mostly Sunny then Slight Chance Rain Showers 24% precip
Spring is +59° warmer
Saturday 75° Low 48° Sunny 5% precip
Spring is +56° warmer
Water Chemistry Sampled 1981-05-28

The water at Granite Creek Hot Spring is alkaline (pH 9.4).

pH 9.4 Alkaline
pH influences mineral absorption through skin
Calcium 2 mg/L
May support bone density and joint health
Magnesium 0 mg/L
Known for muscle relaxation and stress relief
Sodium 52 mg/L
Supports circulation and skin hydration
Sulfate 26 mg/L
Traditionally used for skin conditions and inflammation
Chloride 2 mg/L
Natural antiseptic with skin health benefits
Where to Stay

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Nearby Camping
Barber Flat Cabin (Boise National Forest, Id) 6.9 mi away

Overview The Barber Flat Cabin site was established for administrative use by the Forest Service in 1923, and was used prior to that by the Barber Lumber Company. At the time, the Forest Service used a cabin already on-site as a guard station and then built a new one in 1927. The current cabin and outbuildings were built by the Civilian Conservation Corps in 1935, and the cabin today looks much as it did back then. Guests can drive to Barber Flat Cabin in two-wheel drive passenger cars or tr...

Reservable Yes
Reserve on Recreation.gov →
Temperature
131°F
Warm Hot Boiling
Water Temp 131°F (55°C)
Avg Air Temp 46°F
Above Ambient +85°F
Great soaking conditions September
Access
Open
Road Access Roadside
Nearest Road Middle Fork Road
Distance to Road 237 ft
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 Granite Creek Hot Spring?
Granite Creek Hot Spring has a water temperature of 131°F (55°C). This is considered a hot spring, well above body temperature.
Where is Granite Creek Hot Spring located?
Granite Creek Hot Spring is located in Boise County, Idaho at 4,205 feet elevation, near Idaho City. Coordinates: 43.8030°N, 115.4010°W.
How do I get to Granite Creek Hot Spring?
Granite Creek Hot Spring has Roadside road access, with the nearest road being Middle Fork Road (237 ft from the road).
Is Granite Creek Hot Spring free to visit?
Granite Creek Hot Spring has Open access. It is managed by US Forest Service.
Can I camp near Granite Creek Hot Spring?
Yes, Barber Flat Cabin (Boise National Forest, Id) is located nearby (6.9 miles away).
What minerals are in the water at Granite Creek Hot Spring?
Water chemistry analysis shows the presence of pH, Calcium, Magnesium, Sodium, Sulfate, Chloride. The pH is 9.4 (alkaline).
Is it safe to soak at Granite Creek Hot Spring?
With care. At 131°F Granite Creek 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