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.
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.
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.
Is South Fork Plunge worth visiting?
Best for
- Hot spring soaking
- Overnight camping trips
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...