At 169°F, the source water at Boulder 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.
File:Boulder Hot Springs, July 2010.JPG — cc by-sa 3.0
Boulder Hot Springs ranks among Montana's hottest natural thermal features at 169°F, confirmed by USGS measurement at 74.4°C. The water is strongly alkaline (pH 8.8) with sodium-dominant chemistry at 120 mg/L sodium and very low calcium (2.3 mg/L). It surfaces at 4,880 feet elevation in Jefferson County, 190 meters from the road.
The spring emerges in the Boulder River valley southeast of Helena, where the Elkhorn Mountains meet the northern edge of the Boulder Batholith. Rolling grassland and scattered conifer groves define the valley floor at this elevation. Annual snowfall averages 57.5 inches, and precipitation totals about 20 inches. The town of Boulder sits a few miles north in a broad intermontane basin. Radon-bearing granitic bedrock underlies much of the area, and the extreme water temperature reflects deep circulation through fractured plutonic rock.
History of Boulder Hot Springs
Boulder Hot Springs has operated as a resort since the 1860s, making it one of Montana's oldest continuously used thermal sites. The current lodge building, constructed in stages between 1882 and 1920, is listed on the National Register of Historic Places. The property has functioned as a hotel, hospital, and retreat center at various points. The high sodium and low calcium chemistry produces soft, silky water that distinguished the resort from competing Montana hot spring destinations.
The spring itself is far too hot for direct contact at 169°F -- bathing occurs only in managed, cooled pools at the resort facility. Check current operating hours and reservation requirements before visiting, as the property has changed ownership and operating models multiple times. Boulder is accessible year-round via Interstate 15. The nearest reservable public campground is Sheepshead Picnic Area, 29 km away. Helena, 30 miles northwest, provides full urban services.
Is Boulder Hot Springs worth visiting?
Best for
Observing powerful hot springs
Overnight camping trips
Not ideal for
Casual soaking
Boulder Hot Springs is well suited for observing powerful hot springs and overnight camping trips.
Monthly Climate
21°Jan
20°Feb
30°Mar
38°Apr
49°May
58°Jun
67°Jul
67°Aug
57°Sep
42°Oct
29°Nov
19°Dec
Annual Precip: 20.2 inAnnual Snow: 57.5 in
Best Time to Visit
DecemberAir 19°F · Water 169°F · +150° contrast
FebruaryAir 20°F · Water 169°F · +149° contrast
JanuaryAir 21°F · Water 169°F · +148° contrast
December offers 48°F more contrast than August
USGS Field Measurements
Recent Temperature
165.9°F
(74.4°C)Measured Apr 27, 1976
Water ChemistrySampled 1976-04-27
The water at Boulder Hot Springs is alkaline (pH 8.8).
Overview
Sheepshead Pavilion is available for reservations for private gatherings from mid-June through Labor Day weekend. The pavilion will accommodate about 200 people. It includes picnic tables, barbecue grills and water. There is no electricity to the pavilion, if electricity is needed please bring a generator.
Fees are based on group size:
$75 per day for groups 1-50
$125 per day for groups 51-100
$200 per day for groups 101-200
With a 2+ day reservation, overnight use may be granted,...
What is the water temperature at Boulder Hot Springs?
Boulder Hot Springs has a water temperature of 169°F (76°C). This is considered a hot spring, well above body temperature.
Where is Boulder Hot Springs located?
Boulder Hot Springs is located in Jefferson County, Montana at 4,880 feet elevation, near Boulder. Coordinates: 46.1980°N, 112.0940°W.
How do I get to Boulder Hot Springs?
Boulder Hot Springs has Short Walk road access (0.1 mi from the road).
Can I camp near Boulder Hot Springs?
Yes, Sheepshead Picnic Area is located nearby (18.0 miles away).
What minerals are in the water at Boulder Hot Springs?
Water chemistry analysis shows the presence of pH, Calcium, Magnesium, Sodium, Sulfate, Chloride, Iron. The pH is 8.8 (alkaline).
Is it safe to soak at Boulder Hot Springs?
The water at Boulder 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. Access may be on private land or unconfirmed — verify current conditions before visiting. Always tell someone your plans before visiting remote hot springs.
Is Boulder Hot Springs crowded?
Boulder Hot Springs sees varying levels of visitors depending on the season and day of the week.
What should I bring to Boulder Hot Springs?
Essentials for Boulder Hot Springs: swimsuit, towel, water bottle, warm layers for before and after soaking, 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.
