At 169°F, the source water at Ninemeyer 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.
Ninemeyer Hot Springs reaches a scalding 169°F along Middle Fork Road in Boise National Forest, making it one of Idaho's hottest accessible thermal features. Just 440 feet from the road at 3,760 feet elevation near Idaho City, it runs a staggering 120 degrees above the local average air temperature. Direct contact with the source is dangerous.
The spring emerges in the Middle Fork Boise River canyon, where steep, forested walls channel the drainage through Boise County's rugged interior. The canyon receives over 30 inches of rain and 10 feet of snow annually, feeding dense stands of Douglas fir and ponderosa pine. Steam rises visibly from the source in cooler months, and mineral deposits stain the surrounding rock. Ninemeyer Campground sits just 650 feet away, though a recent wildfire has stripped it of amenities including developed fire rings.
History of Ninemeyer Hot Springs
USGS measurements confirm source temperatures of 76°C with a pH of 9.6, among the most alkaline thermal waters in Idaho. The chemistry reads like a textbook deep-circulation system: calcium nearly absent at 1.6 mg/L, magnesium effectively zero, and sodium dominant at 64 mg/L. These signatures indicate water that has traveled miles underground through the Idaho Batholith's granitic rock before reaching the surface along Middle Fork faults.
The spring is a short walk from Middle Fork Road (Forest Road 268), but the 169°F source water causes severe burns on contact. Observe from a safe distance. Ninemeyer Campground is steps away but currently has no amenities due to wildfire damage and no fires are permitted during Stage 1 restrictions. The road is accessible by car in good weather from mid-May through late September but can be rough. Bring all supplies.
Is Ninemeyer Hot Springs worth visiting?
Best for
Observing powerful hot springs
Overnight camping trips
Not ideal for
Casual soaking
Ninemeyer Hot Springs is well suited for observing powerful hot springs and overnight camping trips.
Monthly Climate
29°Jan
31°Feb
38°Mar
43°Apr
53°May
64°Jun
75°Jul
74°Aug
63°Sep
49°Oct
36°Nov
27°Dec
Annual Precip: 30.1 inAnnual Snow: 122.0 in
Best Time to Visit
DecemberAir 27°F · Water 169°F · +142° contrast
JanuaryAir 29°F · Water 169°F · +140° contrast
FebruaryAir 31°F · Water 169°F · +138° contrast
December offers 48°F more contrast than July
USGS Field Measurements
Recent Temperature
168.8°F
(76.0°C)Measured Aug 19, 1982
Water ChemistrySampled 1982-08-19
The water at Ninemeyer Hot Springs is alkaline (pH 9.6) with 245 mg/L total dissolved solids.
Overview:Due to a wildfire, there are no amenities at the campground. Currently there are no developed campfire rings therefore when Stage 1 fire restrictions area in effect, no fires are permitted.A stay at Ninemeyer Campground enables guests to enjoy all the beauty and recreation offered along the (Middle Fork Boise River Road) Forest Service (FS) Road 268. Weather is usually good from mid-May through late September and is easily accessible by car in good weather, although the road is some...
What is the water temperature at Ninemeyer Hot Springs?
Ninemeyer Hot Springs has a water temperature of 169°F (76°C). This is considered a hot spring, well above body temperature.
Where is Ninemeyer Hot Springs located?
Ninemeyer Hot Springs is located in Boise County, Idaho at 3,760 feet elevation, near Idaho City. Coordinates: 43.7550°N, 115.5710°W.
How do I get to Ninemeyer Hot Springs?
Ninemeyer Hot Springs has Short Walk road access, with the nearest road being Middle Fork Road (440 ft from the road).
Is Ninemeyer Hot Springs free to visit?
Ninemeyer Hot Springs has Open access. It is managed by US Forest Service.
Can I camp near Ninemeyer Hot Springs?
Yes, Ninemeyer Campground is located nearby (0.1 miles away).
What minerals are in the water at Ninemeyer Hot Springs?
Water chemistry analysis shows the presence of pH, Total Dissolved Solids, Calcium, Magnesium, Sodium, Sulfate, Chloride. The pH is 9.6 (alkaline). Total dissolved solids measure 245 mg/L.
Is it safe to soak at Ninemeyer Hot Springs?
The water at Ninemeyer Hot Springs reaches 169°F, which can cause severe burns. Do not enter the source pool directly — look for cooled side pools or downstream areas where the water has cooled to a safe temperature. Always tell someone your plans before visiting remote hot springs.
Is Ninemeyer Hot Springs crowded?
Ninemeyer Hot Springs sees varying levels of visitors depending on the season and day of the week.
What should I bring to Ninemeyer Hot Springs?
Essentials for Ninemeyer Hot Springs: swimsuit, towel, water bottle, camping gear, a trash bag to pack out what you pack in. The water is over 110°F — test the temperature before entering and watch for scalding near the source.
Temperature
169°F
WarmHotBoiling
Water Temp169°F (76°C)
Avg Air Temp49°F
Above Ambient+121°F
Perfect soaking weatherMarch
Access
Open
Road AccessShort Walk
Nearest RoadMiddle Fork Road
Distance to Road440 ft
Land
OwnershipFederal
AgencyUS Forest Service
DesignationNational Forest
UnitBoise National Forest
ManagerUS Forest Service
Protection3 - Protected, subject to extractive use