South Fork Plunge
South Fork Plunge, known locally as Molly's Tub, pushes 129-degree water to the surface in the Boise National Forest, running 87 degrees above ambient air temperature. A short walk of roughly 1,150 feet from South Fork Road delivers soakers to one of Valley County's most rewarding thermal features.
At 5,360 feet elevation near Warm Lake, the spring emerges in a forest corridor that receives over 17 feet of snow annually. The surrounding Boise National Forest canopy filters light across the water, and the temperature differential between the 129-degree source and the 41.7-degree average air creates visible steam on cool mornings. The short trail from South Fork Road passes through mixed conifers, arriving at a thermal area where hot water can be mixed with creek water for comfortable soaking temperatures.
The walk from South Fork Road takes about five minutes. Water at the source is too hot for direct contact at 129 degrees, so look for pools where hot spring water mixes with cooler creek water. Picnic Point Campground at Warm Lake sits less than two miles away and accepts reservations. The area is typically accessible from late June through October, though snow can linger into July in heavy years.
This spring sits along the South Fork of the Salmon River drainage, where deep faults in the Idaho Batholith provide pathways for groundwater to circulate miles below the surface before returning superheated. The Warm Lake area holds multiple thermal features, all products of the same geothermal system. The Forest Service maintains open public access under a protection status that balances recreation with resource management.
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Overview Picnic Point Campground is located on a bluff overlooking beautiful Warm Lake, at an elevation of 5,300 feet. Visitors enjoy boating, fishing, swimming, hiking and viewing local wildlife. Recreation Warm Lake offers great fishing opportunities for cutthroat, rainbow, lake and bull trout. Boating, canoeing and swimming are popular activities. A boat ramp is located at neighboring Shoreline Campground. Billy Rice Swim Beach is within walking distance, offering a day-use site for picni...
South Fork Plunge sits at 5,360 feet above sea level, way above the mile-high mark. You may not feel the altitude strongly, but hot water still dehydrates you faster at elevation. UV is about 21% stronger than at sea level, so bring sunscreen and drink more water than you normally would.
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South Fork Plunge is road-accessible, so you can bring more gear. The water runs hot, so extra hydration is key. Cold air temperatures make a changing robe or warm layers essential.
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