Milford Sweat Hot Spring
Milford Sweat Hot Spring sits inside Craters of the Moon National Preserve, on National Park Service ground in Blaine County, a bit over a hundred yards from the Idaho Medal of Honor Highway. The water runs hot, hotter than a bath you would want to stay in, and the nearest town of any size is Bellevue, about twenty-five miles away. The access entry reads open, though this is Park Service land and its rules govern what happens on it.
Dry country. The preserve sees little precipitation and snow measured in a few feet, which at five thousand feet is enough to make winter travel a question. The walk from the highway is short, a few hundred feet. The land designation in the record is a national conservation area, and the owner is the National Park Service, a different management posture from the Forest Service and BLM springs elsewhere in the state.
December through February carry the best-months tag, which fits cold air and hot water. The source is above comfortable soaking temperature, so test it before any part of you goes in. No campground is on file nearby. No charge is listed. The water chemistry comes from a single sample taken in 1989 and the temperature could have shifted since, so treat both as a starting point.
The Park Service holds it as part of Craters of the Moon National Preserve, and the USGS keeps a site record for it that includes a sample from March 1989.
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 Milford Sweat Hot Spring.
Drag the handle to compare the two views. The orange dot marks the spring, in a frame about three quarters of a mile wide.
- Setting
- Gentle slope
- The ground tilts gently up to the north.
- Highest ground nearby
- 143 ft above the spring
- Within a quarter mile, to the north
A slice through the ground from south to north, about 0.6 miles end to end.
Elevation data: USGS 3D Elevation Program. Aerial imagery: USGS The National Map. Public domain.
That's about twice the US average of 65. It's higher than at 90% 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.
See every spring on the geothermal heat map →
Heat flow estimate: Stanford Thermal Earth Model (Aljubran & Horne, 2024), CC BY 4.0.
The water at Milford Sweat Hot Spring is neutral (pH 7.0).
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Milford Sweat Hot Spring is road-accessible, so you can bring more gear. The water runs hot, so extra hydration is key.
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