Ashton Warm Spring
Ashton Warm Spring emerges at 79 degrees Fahrenheit in Fremont County, placing it below typical soaking temperature but above the surrounding creeks fed by snowmelt. With a near-neutral pH of 7.9 and trace iron content, the water carries a faintly mineral character. A short walk of about 160 meters from Idaho Medal of Honor Highway reaches the source.
The spring sits at 5,200 feet where the upper Snake River Plain transitions into the forested foothills approaching Yellowstone country. Lodgepole pine and mixed conifers frame the approach. Annual snowfall averages over five feet, and the ground stays white well into spring. Summer days are mild, rarely exceeding the mid-80s. The warm water contrasts sharply with the cold streams draining the nearby Caribou-Targhee National Forest.
This stretch of eastern Idaho lies along the western margin of the Yellowstone volcanic system, where deep heat gradually diminishes with distance from the caldera. Ashton itself was established as a railroad town in 1906 and became a gateway to Yellowstone's western entrances. The spring's moderate temperature reflects shallower circulation through fractured volcanic rock rather than contact with deep magmatic heat sources.
A short walk from Idaho Medal of Honor Highway leads to the spring, though the path may be uneven. Warm River Campground, 12 miles away in the Caribou-Targhee National Forest, offers reservable sites and river tubing. Water temperature sits below comfortable soaking range for most visitors, functioning better as a foot soak or curiosity. Best visited June through September when roads and trails are clear.
Is Ashton Warm Spring worth visiting?
Best for
- Overnight camping trips
The water at Ashton Warm Spring is slightly alkaline (pH 7.9).
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Overview Warm River Campground is located on its namesake in the Caribou-Targhee National Forest of southwestern Idaho. Visitors love the campground for its river tubing opportunities. Fishing and hiking are popular as well. Recreation Warm River is a popular location for tubing and fishing. Anglers cast for whitefish, brook, rainbow and cutthroat trout. Numerous hiking, mountain biking and horseback riding trails are in the immediate area, leading to natural springs, waterfalls and old rai...