# Sunflower Flat Hot Spring, Idaho

Sunflower Flat Hot Spring in Idaho. 109°F (43°C). Short Walk · Public Land. Custer County.

- Page: https://www.soakingsprings.com/hot-springs/idaho/sunflower-flat-hot-spring
- Source: Soaking Springs, researched and maintained by Armen Suny
- Updated: 2026-09-14

## Can you soak at Sunflower Flat Hot Spring?

The water leaves the ground at 109°F, a comfortable soaking temperature. It's a short walk from the road. It's on US Forest Service land. We haven't confirmed whether it has a pool or charges a fee.

## Key facts

| Fact | Value |
|---|---|
| Source water temperature | 109°F (43°C) (USGS record; developed pools are often cooled) |
| pH | 9.2 (Alkaline) |
| Elevation | 4,480 ft |
| Access | Short Walk · Public Land, 0.9 mi from the nearest road |
| Land | Challis National Forest, US Forest Service |
| County | Custer County |
| Nearest town | Challis |
| Coordinates | 44.73300, -115.01800 |
| Best months to soak | December, January, February (largest gap between water and average air temperature) |
| Nearest campground | BOUNDARY CREEK CAMPGROUND, 19.4 mi |

## About Sunflower Flat Hot Spring

Sunflower Flat Hot Spring comes out at soaking temperature, around 109 degrees, on Challis National Forest ground, Custer County, about 42 miles from Challis. It is open to the public; count on a little under a mile on foot. A separate spring with a nearly identical name, Sunflower Hot Springs, appears in the same county and runs much hotter.

Around 4,500 feet, with ninety-eight inches of snowfall in an average year and about 22 inches of precipitation; mid forties is the yearly average. Forest Service acreage. Road to water is nine tenths of a mile on foot, and no road name is recorded. Beyond the National Forest label the record carries no designation.

Winter is the listed best season. Boundary Creek Campground, almost twenty miles out, is the closest camping on record. Water chemistry and temperature date to a June 1980 USGS sample, alkaline water in the soaking range. Check it with a hand before settling in, since the reading sits at the warm end of comfortable.

## Water chemistry

Lab sample from 1980-06-27 (Water Quality Portal).

| Measure | Value |
|---|---|
| pH | 9.2 |
| Calcium | 4.4 mg/L |
| Magnesium | 0.1 mg/L |
| Sodium | 97 mg/L |
| Sulfate | 110 mg/L |
| Chloride | 13 mg/L |

## Nearby

- Nearest city page: [Hot springs near Challis](https://www.soakingsprings.com/hot-springs/near/idaho/challis), 34 mi away
- State page: [Hot springs in Idaho](https://www.soakingsprings.com/hot-springs/idaho)
- [Thomas Creek Ranch Hot Spring, ID](https://www.soakingsprings.com/hot-springs/idaho/thomas-creek-ranch-hot-spring): 138°F source, pH 9.3, Short Walk, near Challis, Custer County
- [Sunflower Hot Springs, ID](https://www.soakingsprings.com/hot-springs/idaho/sunflower-hot-springs): 149°F source, pH 9.3, Short Walk, near Challis, Custer County, primitive pools
- [Indian Creek Hot Spring, ID](https://www.soakingsprings.com/hot-springs/idaho/indian-creek-hot-spring): 190°F source, pH 9.0, Hike, near Challis, Custer County
- [Middle Fork Indian Creek Hot Spring, ID](https://www.soakingsprings.com/hot-springs/idaho/middle-fork-indian-creek-hot-spring): 162°F source, pH 9.0, Hike, near Challis, Custer County
- [Cox Hot Springs, ID](https://www.soakingsprings.com/hot-springs/idaho/cox-hot-springs): 131°F source, pH 8.9, Hike, near Challis, Custer County
- [Pistol Creek Hot Springs, ID](https://www.soakingsprings.com/hot-springs/idaho/pistol-creek-hot-springs): 115°F source, pH 9.6, Hike, near Cascade, Valley County

## Questions

**What is the water temperature at Sunflower Flat Hot Spring?**
Sunflower Flat Hot Spring has a water temperature of 109°F (43°C). This is considered a hot spring, well above body temperature.

**Where is Sunflower Flat Hot Spring located?**
Sunflower Flat Hot Spring is located in Custer County, Idaho at 4,480 feet elevation, near Challis. Coordinates: 44.7330°N, 115.0180°W.

**How do I get to Sunflower Flat Hot Spring?**
Sunflower Flat Hot Spring has Short Walk road access (0.9 mi from the road).

**Is Sunflower Flat Hot Spring free to visit?**
Sunflower Flat Hot Spring has Open access. It is managed by US Forest Service.

**Can I camp near Sunflower Flat Hot Spring?**
Yes, Boundary Creek Campground is located nearby (19.4 miles away).

**What minerals are in the water at Sunflower Flat Hot Spring?**
Water chemistry analysis shows the presence of pH, Calcium, Magnesium, Sodium, Sulfate, Chloride. The pH is 9.2 (alkaline).

## Sources

- USGS thermal springs records, Water Quality Portal lab analyses, OpenStreetMap, Wikipedia/Wikidata, NOAA climate normals
- https://en.wikipedia.org/wiki/Sunflower_Hot_Springs