Donlay Ranch Hot Spring

Boise County, Idaho · Near Idaho City
44.0440°N, 115.8510°W · 3,200 ft
131°F 35°F air · Good soaking weather 3,200 ft Open Roadside US Forest Service Camping nearby (3.5 mi)
Aerial view of the ground around Donlay Ranch Hot Spring LiDAR bare-earth view of the same ground around Donlay Ranch Hot Spring
Aerial LiDAR bare earth

Drag the handle to compare the two views. The orange dot marks the spring, in a frame about three quarters of a mile wide.

Donlay Ranch Hot Spring occupies Boise National Forest ground in Boise County, 15 miles or so from Idaho City, on Southfork Road. Low 130s water, which needs cooling before a soak. Access is open. A campground called Hot Springs sits about 3.5 miles away, the closest developed camping on file, which makes this an easy overnight.

Location

Southfork Road passes about 115 feet from the spring. The site is low for the Boise forest, but the snow still piles up, close to nine feet most winters, in a wet climate. Beyond that the ground is undescribed, and no image is on record.

The best-months note points to December through February. Nine feet or so of snow comes down most years, so ask about the forest road before you drive. Fees and any kind of structure at the spring go unmentioned on file. The chemistry dates from 1978 and came back alkaline. Hot Springs campground is close enough to base from, with Idaho City the closest town.

Terrain

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 Donlay Ranch Hot Spring.

Setting
Canyon floor
Steep ground climbs away on both sides of the spring.
Highest ground nearby
658 ft above the spring
Within a quarter mile, to the north
Cross-section through the spring

A slice through the ground from north to south, about 0.6 miles end to end.

Elevation data: USGS 3D Elevation Program. Aerial imagery: USGS The National Map. Public domain.

Heat Below
128 milliwatts per square meter of heat flow

That's about twice the US average of 65. It's higher than at 78% 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.

Heat flow estimate: Stanford Thermal Earth Model (Aljubran & Horne, 2024), CC BY 4.0.

Monthly Climate
28°
Jan
32°
Feb
39°
Mar
45°
Apr
55°
May
64°
Jun
75°
Jul
74°
Aug
64°
Sep
49°
Oct
37°
Nov
27°
Dec
Annual Precip: 30.9 in Annual Snow: 105.6 in
Best Time to Visit
December Air 27°F · Water 131°F · +104° contrast
January Air 28°F · Water 131°F · +103° contrast
February Air 32°F · Water 131°F · +99° contrast
December offers 48°F more contrast than July
Current Conditions
35°F
S 0.0 mph 93% Good soaking weather
Today 76° Low 41° Sunny
Spring is +55° warmer
Wednesday 84° Low 46° Sunny
Spring is +47° warmer
Thursday 75° Low 43° Rain Showers Likely 74% precip
Spring is +56° warmer
Friday 75° Low 42° Areas Of Fog 20% precip
Spring is +56° warmer
Saturday 79° Low 43° Sunny 5% precip
Spring is +52° warmer
Water Chemistry Sampled 1978-11-27

The water at Donlay Ranch Hot Spring is alkaline (pH 9.2).

pH 9.2 Alkaline
pH influences mineral absorption through skin
Calcium 2 mg/L
May support bone density and joint health
Magnesium 0 mg/L
Known for muscle relaxation and stress relief
Sodium 75 mg/L
Supports circulation and skin hydration
Sulfate 38 mg/L
Traditionally used for skin conditions and inflammation
Chloride 6 mg/L
Natural antiseptic with skin health benefits
Nearby Camping
Nearby Camping
Hot Springs 3.5 mi away

Overview Hot Springs Campground is located just east of Garden Valley, Idaho along the Banks-Lowman Highway at an elevation of 3169 feet. Visitors enjoy rafting, kayaking, fishing on the South Fork Payette River, and soaking in the hot springs at the river's edge. Recreation The South Fork Payette River is across the road from the campground, offering fishing, whitewater rafting, and kayaking. A natural hot springs soaking pool is located on the river directly across the road and down a...

Reservable Yes
Reserve on Recreation.gov →
Temperature
131°F
Warm Hot Boiling
Water Temp 131°F (55°C)
Avg Air Temp 49°F
Above Ambient +82°F
Great soaking conditions September
Access
Open
Road Access Roadside
Nearest Road Southfork Road
Distance to Road 115 ft
Land
Ownership Federal
Agency US Forest Service
Designation National Forest
Unit Boise National Forest
Manager US Forest Service
Protection 3 - Protected, subject to extractive use
Frequently Asked Questions
What is the water temperature at Donlay Ranch Hot Spring?
Donlay Ranch Hot Spring has a water temperature of 131°F (55°C). This is considered a hot spring, well above body temperature.
Where is Donlay Ranch Hot Spring located?
Donlay Ranch Hot Spring is located in Boise County, Idaho at 3,200 feet elevation, near Idaho City. Coordinates: 44.0440°N, 115.8510°W.
How do I get to Donlay Ranch Hot Spring?
Donlay Ranch Hot Spring has Roadside road access, with the nearest road being Southfork Road (115 ft from the road).
Is Donlay Ranch Hot Spring free to visit?
Donlay Ranch Hot Spring has Open access. It is managed by US Forest Service.
Can I camp near Donlay Ranch Hot Spring?
Yes, Hot Springs is located nearby (3.5 miles away).
What minerals are in the water at Donlay Ranch Hot Spring?
Water chemistry analysis shows the presence of pH, Calcium, Magnesium, Sodium, Sulfate, Chloride. The pH is 9.2 (alkaline).
Is it safe to soak at Donlay Ranch Hot Spring?
With care. At 131°F Donlay Ranch Hot Spring is hot enough to need short sessions, fifteen to twenty minutes, and plenty of water. Enter slowly and get out if you feel light-headed.
Sources: USGS NWIS