Twin Springs
Twin Springs reaches 151°F at the surface — confirmed at 67°C by USGS — making it one of Idaho's hottest thermal features. The spring sits directly beside North Fork Boise River Road, less than 3 meters from the pavement, in the Boise National Forest at 3,440 feet elevation. Total dissolved solids measure 217 mg/L with pH at 9.5.
The spring emerges along the North Fork of the Boise River in Boise County, where a narrow canyon carved through granitic and metamorphic rock channels both the river and the road through dense conifer forest. At 3,440 feet, the setting is mid-elevation mountain terrain with 74.6 inches of annual snow and an average temperature of 49.4°F. The river corridor supports riparian vegetation including alder and willow, while Douglas fir and ponderosa pine cover the canyon walls above.
The name Twin Springs suggests a dual-source discharge, though specific documentation of the feature's history is limited. The spring sits near Idaho City, the center of the 1862 Boise Basin gold rush, which was briefly one of the largest cities in the Pacific Northwest. The North Fork Boise River Road has provided access to this drainage for over a century, and the Forest Service has managed the surrounding land as part of Boise National Forest since 1908.
Water at 151°F is dangerously hot and will cause severe burns on contact — do not enter the source pool. Any soaking requires mixing with river water downstream. Access is available from late spring through fall; the road may close in winter due to snow. Ninemeyer Campground, 14 km away, provides primitive first-come sites but currently lacks amenities due to wildfire damage. The road is accessible by car in good weather but can be rough.
Is Twin Springs worth visiting?
Best for
- Observing powerful hot springs
- Easy day trips
- Overnight camping trips
Not ideal for
- Casual soaking
The water at Twin Springs is alkaline (pH 9.5) with 217 mg/L total dissolved solids.
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...