Twin Springs

Boise County, Idaho · Near Idaho City
43.6710°N, 115.6960°W · 3,440 ft
151°F 35°F air · Good soaking weather 3,440 ft Open Roadside US Forest Service Camping nearby (8.6 mi)
Very Hot Source, Use Extreme Caution

At 151°F, the source water at Twin Springs is hot enough to cause burns. Some hot springs this hot have cooler side pools or downstream areas suitable for soaking. Always test the water temperature before entering.

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

Twin Springs is a scalding source on North Fork Boise River Road in Boise National Forest, about thirteen miles from Idaho City. The water comes out hot enough to burn skin on contact, so this is a thermal feature to look at, and to enter only in spots where the heat has drained out of it. Access is listed as open. Low dissolved solids and a high pH characterize the sample on file.

Location

The road passes essentially on top of the spring, nine feet away by the measurement on file, and the walk is a matter of a few steps. This is Forest Service land at around thirty-four hundred feet. Snowfall is moderate, about seventy-five inches, in a fairly dry climate.

The record's pick for timing is the dead of winter. Ninemeyer Campground is about nine miles off. Since the spring sits on the road shoulder, no walking is involved. The water leaves the ground scalding. Do not step in anywhere you have not tested, and keep children and dogs back from the outflow. The figures come from a May 1981 survey.

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 Twin Springs.

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

That's about twice the US average of 65. It's higher than at 88% 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
28°
Jan
32°
Feb
39°
Mar
45°
Apr
55°
May
65°
Jun
75°
Jul
74°
Aug
64°
Sep
50°
Oct
37°
Nov
28°
Dec
Annual Precip: 25.3 in Annual Snow: 74.6 in
Best Time to Visit
December Air 28°F · Water 151°F · +124° contrast
January Air 28°F · Water 151°F · +123° contrast
February Air 32°F · Water 151°F · +119° contrast
December offers 48°F more contrast than July
Current Conditions
35°F
S 0.0 mph 93% Good soaking weather
Today 78° Low 48° Sunny
Spring is +73° warmer
Wednesday 84° Low 53° Sunny
Spring is +67° warmer
Thursday 76° Low 48° Showers And Thunderstorms Likely 69% precip
Spring is +75° warmer
Friday 77° Low 47° Mostly Sunny then Slight Chance Rain Showers 16% precip
Spring is +74° warmer
Saturday 80° Low 49° Sunny 4% precip
Spring is +71° warmer
Water Chemistry Sampled 1981-05-27

The water at Twin Springs is alkaline (pH 9.5) with 217 mg/L total dissolved solids.

pH 9.5 Alkaline
pH influences mineral absorption through skin
Higher mineral concentration for therapeutic soaking
Calcium 2 mg/L
May support bone density and joint health
Magnesium 0 mg/L
Known for muscle relaxation and stress relief
Sodium 49 mg/L
Supports circulation and skin hydration
Sulfate 21 mg/L
Traditionally used for skin conditions and inflammation
Chloride 2 mg/L
Natural antiseptic with skin health benefits
Iron 20 µg/L
Iron-rich springs may support circulation
Where to Stay

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Nearby Camping
Ninemeyer Campground 8.6 mi away

Overview:Due to a wildfire, there are no amenities at the campground.  Currently there are no developed campfire rings therefore when Stage 1 fire restrictions area in effect, no fires are permitted.A stay at Ninemeyer Campground enables guests to enjoy all the beauty and recreation offered along the (Middle Fork Boise River Road) Forest Service (FS) Road 268. Weather is usually good from mid-May through late September and is easily accessible by car in good weather, although the road is some...

Reserve on Recreation.gov →
Temperature
151°F
Warm Hot Boiling
Water Temp 151°F (66°C)
Avg Air Temp 49°F
Above Ambient +102°F
Great soaking conditions September
Access
Open
Road Access Roadside
Nearest Road North Fork Boise River Road
Distance to Road 9 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 Twin Springs?
Twin Springs has a water temperature of 151°F (66°C). This is considered a hot spring, well above body temperature.
Where is Twin Springs located?
Twin Springs is located in Boise County, Idaho at 3,440 feet elevation, near Idaho City. Coordinates: 43.6710°N, 115.6960°W.
How do I get to Twin Springs?
Twin Springs has Roadside road access, with the nearest road being North Fork Boise River Road (9 ft from the road).
Is Twin Springs free to visit?
Twin Springs has Open access. It is managed by US Forest Service.
Can I camp near Twin Springs?
Yes, Ninemeyer Campground is located nearby (8.6 miles away).
What minerals are in the water at Twin Springs?
Water chemistry analysis shows the presence of pH, Total Dissolved Solids, Calcium, Magnesium, Sodium, Sulfate, Chloride, Iron. The pH is 9.5 (alkaline). Total dissolved solids measure 217 mg/L.
Is it safe to soak at Twin Springs?
No, not at the source. The water at Twin Springs reaches 151°F, which can cause severe burns within seconds. Look for cooled side pools or downstream stretches, and test with a hand before anything else.
Sources: USGS NWIS