Entry No. 9 — the Missoula file — filed under: soak
Nimrod Warm Springs
This is a completely undeveloped warm spring on private land where the family owners quietly allow respectful free access. The water hovers around 70 degrees year-round, more refreshing soak than scalding hot tub, in a wild riverside setting. Its strangest feature is an underwater cave you can dive down to and surface inside, a trick reserved for confident swimmers who bring goggles or a light for the murky visibility. There are no facilities, no signs, and no staff, just a genuinely odd natural pool that locals work hard to keep open.
The story
Rushing down Interstate 90 east of Missoula, most drivers miss the pull-off entirely. Right off the highway near Bearmouth and Drummond Frontage Road, Nimrod Warm Springs doesn't fit the standard Montana hot spring script. There are no changing rooms, no paid entry, and certainly no steamy 104-degree soak. Instead, water pushes up out of the earth at a steady 70 to 72 degrees year-round, cascading over a small waterfall into a deep, surprisingly clear basin.
The land itself is private property, but the owning family quietly maintains a policy of allowed access—provided people don't ruin it. It lives on a delicate line where local volunteers periodically have to clean up litter to keep the site open. What brings people back, besides the total lack of crowds on a Tuesday afternoon, is the pool's oddest secret: an underwater cave hidden beneath the surface face.
If you drop below the waterline with goggles and a waterproof light, you can swim down and surface inside an air-filled submerged pocket of rock. It’s dark, tight, and murky, making it an unsettling adrenaline spike for anyone who isn't a strong swimmer.
What it's like
Drive down the Drummond Frontage Road near mile marker 138 on I-90 and look for an unmarked pullout along the riverbank. There are zero amenities—no trash cans, no restrooms, and no signs telling you you've arrived. The water feels cold at first contact compared to hot springs, but once you get moving in the pool, it feels like a heated swimming pool. Bring dive goggles, a waterproof flashhead if you intend to duck into the cave, and a trash bag to pack out everything you bring.
The move: Drive out on a warm afternoon for a low-key wild soak, and if you are strong swimmers, take turns ducking down to the hidden underwater cave.
📍 Before you go On private property; access is a courtesy, so pack out everything and be respectful or access may close. The underwater cave is for expert swimmers only. Water is warm (~70F), not hot; no facilities of any kind.
- 📍 Nimrod / Bearmouth (east of Missoula)
- 💸 Free
- ⚡ Up for anything
- 🌗 Outdoors
Where: Near Nimrod, off I-90, Granite County, MT
Hours: Added 2026-06-24 — confirm current hours before you go.
⚠ Seasonal or scheduled — always check before you go.
Pair it with
- Garnet Ghost Town — Pair a wild swim in the warm spring with a drive up into the Garnet Range to walk through Montana's best-preserved 1890s mining town.
- Ohrmann Museum & Gallery — After swimming, continue east down I-90 to Drummond to see a farmyard full of massive, surreal welded scrap-metal animal sculptures.
- Granite Ghost Town State Park — Head further southeast into Granite County to explore the massive stone mill ruins perched above Philipsburg.
Good to know
How hot is the water at Nimrod Warm Springs?
It hovers between 70°F and 72°F year-round. It is warm enough for comfortable swimming on a hot day, but it is not a steaming hot tub.
Is Nimrod Warm Springs open to the public?
It sits on private property, but the landowners currently allow polite, respectful public access. Respect the land and pack out all trash so access isn't revoked.
How do you access the underwater cave?
You must dive beneath the pool's surface and swim under the rock wall to surface inside an air pocket. It requires goggles or a light due to low visibility and should only be attempted by confident swimmers.
Are there restrooms or facilities on-site?
No. The site is entirely undeveloped with no toilets, trash receptacles, or staff.
Plan a visit & invite your people →
Further reading: discoveringmontana.com · missoulian.com · roamingmontana.com · mtbeyond.com · Official site · Facebook
last checked: 2026-06-24