Rosalys Warm Spring surfaces at 106 degrees Fahrenheit and 6,560 feet elevation near Sun Valley, one of the higher-altitude thermal features in the state. Its pH of 9.4 makes it among the more alkaline springs in Idaho, with just 2.7 mg/L calcium dissolved in the water.
Reaching the spring requires a walk of roughly a quarter mile from the nearest road. The terrain sits in Blaine County high country where annual snowfall averages over 13 feet and the mean air temperature hovers around 39 degrees. The landscape is open and exposed at this elevation, with views across sagebrush meadows toward distant peaks. The mineral-laden water feeds a modest flow into the surrounding drainage.
History of Rosalys Warm Spring
The strongly alkaline chemistry and extremely low calcium suggest the water circulates deep through silicic volcanic rock, stripping sodium and sulfate while leaving calcium behind. At 6,560 feet, the spring occupies terrain shaped by Pleistocene glaciation and subsequent erosion. Outlet Campground near Redfish Lake, about six miles away, anchors the Sawtooth National Recreation Area that defines this stretch of central Idaho.
Access requires a short walk from the road, roughly 1,500 feet. Snow buries this area from late fall through spring, so plan visits between June and October. The nearest reservable campground is Outlet Campground at Redfish Lake, about six miles out. Water temperature is comfortable for soaking without mixing, though conditions vary seasonally.
Is Rosalys Warm Spring worth visiting?
Best for
- Hot spring soaking
- Overnight camping trips
- Winter soaking with dramatic temperature contrast
Rosalys Warm Spring is well suited for hot spring soaking and overnight camping trips.
Annual Precip: 30.0 in
Annual Snow: 161.7 in
December
Air 19°F · Water 106°F · +87° contrast
January
Air 22°F · Water 106°F · +84° contrast
February
Air 23°F · Water 106°F · +83° contrast
December offers 45°F more contrast than July
Recent Temperature
116.6°F
(47.0°C)
Measured Sep 12, 1979
The water at Rosalys Warm Spring is alkaline (pH 9.4).
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
Outlet Campground is located next to beautiful Redfish Lake beneath the Sawtooth Mountain Range at an elevation of 6,500 feet. Recreation
Outlet Campground is in the heart of the beautiful Sawtooth National Recreation Area, where outdoor activities abound. Redfish Lake offers excellent boating, water skiing, canoeing, kayaking and fishing for rainbow trout and Kokanee salmon.
Little Redfish Lake is just down the road, offering additional fishing and canoeing.
In the immediate are...
Reserve on Recreation.gov →
Swimsuit & towel
Water bottle
Stay hydrated, especially in hot water
Warm layers
Cold air before and after soaking
Camping gear
Nearby camping at Outlet Campground
Trash bag
Pack out what you pack in
20 miles from Sun Valley, ID
USGS Quad: OBSIDIAN 7.5 · PP 492: 101.0 · NOAA: 22.0 · AMS Map: CHALLIS
What is the water temperature at Rosalys Warm Spring?
Rosalys Warm Spring has a water temperature of 106°F (41°C). This is considered a hot spring, well above body temperature.
Where is Rosalys Warm Spring located?
Rosalys Warm Spring is located in Blaine County, Idaho at 6,560 feet elevation, near Sun Valley. Coordinates: 44.1010°N, 114.8650°W.
How do I get to Rosalys Warm Spring?
Rosalys Warm Spring has Short Walk road access (0.3 mi from the road).
Can I camp near Rosalys Warm Spring?
Yes, Outlet Campground is located nearby (3.6 miles away).
What minerals are in the water at Rosalys Warm Spring?
Water chemistry analysis shows the presence of pH, Calcium, Sodium, Sulfate, Chloride. The pH is 9.4 (alkaline).
Is it safe to soak at Rosalys Warm Spring?
Rosalys Warm Spring is generally safe for soaking at its recorded temperature. Access may be on private land or unconfirmed — verify current conditions before visiting. Always tell someone your plans before visiting remote hot springs.
Is Rosalys Warm Spring crowded?
Rosalys Warm Spring sees varying levels of visitors depending on the season and day of the week.
What should I bring to Rosalys Warm Spring?
Essentials for Rosalys Warm Spring: swimsuit, towel, water bottle, warm layers for before and after soaking, camping gear, a trash bag to pack out what you pack in.