Bonneville Hot Springs

Boise County, Idaho · Near Idaho City
44.1570°N, 115.3140°W · 4,880 ft
185°F 35°F air · Good soaking weather 4,880 ft Open Short Walk US Forest Service Camping nearby (0.4 mi)
Very Hot Source, Use Extreme Caution

At 185°F, the source water at Bonneville Hot Springs is hot enough to cause burns. Some hot springs this hot have cooler side pools or downstream areas suitable for soaking. Always test the water temperature before entering.

Nobody is putting a hand in this water. Bonneville Hot Springs runs scalding where it surfaces, in the Boise National Forest of Boise County, and the nearest town, Idaho City, sits a long 34 miles off. Access is listed as open. A Forest Service campground of the same name sits close by, so of the places in the forest north of Idaho City, this is one of the easier ones to sleep beside.

Location

You leave the car at the end of Bonneville Trailhead Road and walk about a third of a mile. The spring sits at mid elevation in conifer country and the winters here are heavy. Something close to fifteen feet of snow lands in an average year. The rest of the year brings a fair amount of rain, so this is wet mountain forest, nothing like the sagebrush country further south in the state.

December through February carry the best-months tag on file, which is odd given how much snow falls, so treat that as a note about the water and find out whether the trailhead road is even passable before you drive up. Bonneville campground is under half a mile away. The temperature reading dates from a survey in 1979. Source water that hot will burn you. Nothing on file says whether there is a cooler pool downstream.

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 Bonneville Hot Springs.

Aerial view of the ground around Bonneville Hot Springs LiDAR bare-earth view of the same ground around Bonneville Hot Springs
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.

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

A slice through the ground from west to east, about 0.6 miles end to end.

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

Heat Below
146 milliwatts per square meter of heat flow

That's about twice the US average of 65. It's higher than at 92% 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
27°
Jan
29°
Feb
35°
Mar
39°
Apr
47°
May
58°
Jun
70°
Jul
69°
Aug
59°
Sep
45°
Oct
32°
Nov
24°
Dec
Annual Precip: 33.8 in Annual Snow: 176.2 in
Best Time to Visit
December Air 24°F · Water 185°F · +161° contrast
January Air 27°F · Water 185°F · +158° contrast
February Air 29°F · Water 185°F · +156° contrast
December offers 46°F more contrast than July
Current Conditions
35°F
S 0.0 mph 93% Good soaking weather
Today 72° Low 41° Sunny
Spring is +113° warmer
Wednesday 79° Low 46° Sunny
Spring is +106° warmer
Thursday 72° Low 43° Showers And Thunderstorms 82% precip
Spring is +113° warmer
Friday 71° Low 40° Slight Chance Rain Showers then Areas Of Fog 32% precip
Spring is +114° warmer
Saturday 74° Low 42° Sunny 8% precip
Spring is +111° warmer
Water Chemistry Sampled 1979-03-13

The water at Bonneville Hot Springs is alkaline (pH 9.3).

pH 9.3 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 77 mg/L
Supports circulation and skin hydration
Sulfate 50 mg/L
Traditionally used for skin conditions and inflammation
Chloride 8 mg/L
Natural antiseptic with skin health benefits
Where to Stay

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Nearby Camping
Bonneville 0.4 mi away

Overview Bonneville Campground is 19 miles east of Lowman, Idaho just off Highway 21 at an elevation of 4,700 feet. Warm Springs Creek runs alongside the campground and the South Fork Payette River lies across the highway. Visitors enjoy soaking at Bonneville Hot Springs a short distance above the campground, and fishing in the creek and river.Recreation A 1/4-mile hiking trail leads from the campground to Bonneville Hot Springs, where a soaking pool awaits. Warm Springs Creek offers good tro...

Reservable Yes
Reserve on Recreation.gov →
Temperature
185°F
Warm Hot Boiling
Water Temp 185°F (85°C)
Avg Air Temp 45°F
Above Ambient +140°F
Great soaking conditions September
Access
Open
Road Access Short Walk
Nearest Road Bonneville Trailhead Road
Distance to Road 0.3 mi
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 Bonneville Hot Springs?
Bonneville Hot Springs has a water temperature of 185°F (85°C). This is considered a hot spring, well above body temperature.
Where is Bonneville Hot Springs located?
Bonneville Hot Springs is located in Boise County, Idaho at 4,880 feet elevation, near Idaho City. Coordinates: 44.1570°N, 115.3140°W.
How do I get to Bonneville Hot Springs?
Bonneville Hot Springs has Short Walk road access, with the nearest road being Bonneville Trailhead Road (0.3 mi from the road).
Is Bonneville Hot Springs free to visit?
Bonneville Hot Springs has Open access. It is managed by US Forest Service.
Can I camp near Bonneville Hot Springs?
Yes, Bonneville is located nearby (0.4 miles away).
What minerals are in the water at Bonneville Hot Springs?
Water chemistry analysis shows the presence of pH, Calcium, Magnesium, Sodium, Sulfate, Chloride. The pH is 9.3 (alkaline).
Is it safe to soak at Bonneville Hot Springs?
No, not at the source. The water at Bonneville Hot Springs reaches 185°F, which can cause severe burns within seconds. Look for cooled side pools or downstream stretches, and test with a hand before anything else.
Sources: USGS NWIS