Smith Cabin Hot Spring sits just 65 feet from Middle Fork Road in the Boise National Forest, delivering 138-degree water at 3,560 feet elevation — one of the hottest roadside springs along the Middle Fork Boise River corridor. USGS data confirms 140-degree water with a pH of 9.5 and remarkably low mineral content.
The spring emerges beside the gravel road where the Middle Fork Boise River carves through a narrow, forested canyon in Boise County. Ponderosa pine shade the banks, and the river runs within earshot. The water chemistry is among the purest of any hot spring in the area — just 44 mg/L sodium, 18 mg/L sulfate, and 2 mg/L chloride. Steam drifts across the road surface in cool weather, marking the spring's location before you see it.
History of Smith Cabin Hot Spring
Smith Cabin Hot Spring takes its name from a former forest service or settler cabin that once stood nearby. The spring taps the same deep geothermal corridor that feeds Sheep Creek Bridge and other thermal features along the Middle Fork. Its extreme alkalinity and near-zero calcium and magnesium content indicate water that has spent considerable time circulating through the granitic Idaho Batholith before surfacing.
The spring is immediately roadside — no hiking required. However, the source temperature of 138 degrees is dangerously hot. Look for spots where it meets the river or cooler side streams. Middle Fork Road can be rough and narrow; check seasonal conditions before driving. Ninemeyer Campground is 5.6 km away but has limited amenities due to wildfire damage. Best access is mid-May through late September.
Is Smith Cabin Hot Spring worth visiting?
Best for
- Hot spring soaking
- Easy day trips
- Overnight camping trips
Smith Cabin Hot Spring offers an accessible hot spring experience — great for a day trip.
Annual Precip: 28.8 in
Annual Snow: 110.1 in
December
Air 28°F · Water 138°F · +110° contrast
January
Air 30°F · Water 138°F · +109° contrast
February
Air 32°F · Water 138°F · +106° contrast
December offers 47°F more contrast than July
Recent Temperature
140.0°F
(60.0°C)
Measured Aug 03, 1981
The water at Smith Cabin Hot Spring is alkaline (pH 9.5).
pH influences mineral absorption through skin
May support bone density and joint health
Supports circulation and skin hydration
Traditionally used for skin conditions and inflammation
Natural antiseptic with skin health benefits
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 →
Swimsuit & towel
Water bottle
Stay hydrated, especially in hot water
Camping gear
Nearby camping at Ninemeyer Campground
Trash bag
Pack out what you pack in
Water shoes
Hot ground near source
3 miles from Idaho City, ID
USGS Quad: SHEEP CREEK 7.5 · PP 492: 112.0 · NOAA: 14.0 · AMS Map: HAILEY
What is the water temperature at Smith Cabin Hot Spring?
Smith Cabin Hot Spring has a water temperature of 138°F (59°C). This is considered a hot spring, well above body temperature.
Where is Smith Cabin Hot Spring located?
Smith Cabin Hot Spring is located in Boise County, Idaho at 3,560 feet elevation, near Idaho City. Coordinates: 43.7200°N, 115.6170°W.
How do I get to Smith Cabin Hot Spring?
Smith Cabin Hot Spring has Roadside road access, with the nearest road being Middle Fork Road (65 ft from the road).
Is Smith Cabin Hot Spring free to visit?
Smith Cabin Hot Spring has Open access. It is managed by US Forest Service.
Can I camp near Smith Cabin Hot Spring?
Yes, Ninemeyer Campground is located nearby (3.5 miles away).
What minerals are in the water at Smith Cabin Hot Spring?
Water chemistry analysis shows the presence of pH, Calcium, Sodium, Sulfate, Chloride. The pH is 9.5 (alkaline).
Is it safe to soak at Smith Cabin Hot Spring?
At 138°F, Smith Cabin Hot Spring is hot enough to require caution. Enter slowly, limit soaking sessions to 15–20 minutes, and stay hydrated. Always tell someone your plans before visiting remote hot springs.
Is Smith Cabin Hot Spring crowded?
Smith Cabin Hot Spring is accessible from a paved road, making it easy to reach. Weekends and holidays may be busier — consider visiting on a weekday for a quieter experience.
What should I bring to Smith Cabin Hot Spring?
Essentials for Smith Cabin Hot Spring: swimsuit, towel, water bottle, camping gear, a trash bag to pack out what you pack in. The water is over 110°F — test the temperature before entering and watch for scalding near the source.