Rattlesnake Hot Spring
Rattlesnake Hot Spring runs at 133 degrees Fahrenheit, nearly 86 degrees above the ambient air temperature, making it one of the hotter sources in the Boise National Forest. At 4,216 feet near Idaho City, reaching it requires a mile-plus hike through forested terrain in Boise County.
The trail drops through a mixed conifer forest of ponderosa pine and Douglas fir typical of the middle-elevation Boise basin. The landscape transitions from dry, open ridges to steeper, shadier drainages closer to the spring. Annual precipitation runs around 21 inches with moderate snowfall of about 4.5 feet, keeping conditions drier than Idaho's northern thermal areas. The thermal source is unmistakable, with steam visible in cooler weather.
Boise County hosted Idaho's first major gold rush in the 1860s, and the thermal features around Idaho City were well-known to miners and settlers. Rattlesnake Hot Spring's high temperature reflects deep geothermal circulation through the Idaho Batholith's granitic bedrock, where water descends thousands of feet along fractures before returning to the surface superheated.
The hike in covers roughly 1.1 miles from the nearest road, with some elevation change. The water is far too hot for direct soaking at the source and must cool or be mixed with stream water. Big Roaring River Lake Campground lies about 11 miles away with 12 first-come, first-served sites. Carry adequate water and watch for rattlesnakes in warmer months, true to the spring's name.
Is Rattlesnake Hot Spring worth visiting?
Best for
- Hot spring soaking
- Overnight camping trips
Overview: Set within the beautiful Trinity Recreation area, the Big Roaring River Lake Campground has12 campsites in a dense lodgepole forest on the river.The Trailhead to the north follows the Upper Roaring River and the Trailhead to the south accesses the William H. Pogue National Recreation Trail and the Lava Mountain Trail.Both trails are open to two-wheeled ATVs, horses, bikes, and people. The Lava Mountain Trail itself passes three lovely lakes on its way south to Lava Mountain.Fishing...