Unnamed Thermal Spring
Deep in the San Bernardino National Forest near Mentone, this 90-degree spring flows 26 degrees above ambient in mountains where geothermal activity remains relatively scarce.
The spring emerges at 2,279 feet elevation within a forest of mixed conifers, with Santa Ana Truck Road providing the trailhead for a half-mile approach. Pine and fir trees create a cool, shaded environment where the thermal water offers sharp contrast to the surrounding cold alpine air.
Geologically, this spring indicates circulation through fault systems in the San Bernardino range, where tectonic activity influences groundwater pathways. The U.S. Forest Service manages the site as part of the national forest's multiple-use framework, balancing recreation with resource conservation.
A half-mile hike from Santa Ana Truck Road leads to the spring, placing it in the short-walk category for access. The San Bernardino National Forest experiences significant winter snowfall, so plan visits for late spring through fall. Green Valley Campground offers facilities 13.5 kilometers away.
Is this spring worth visiting?
Best for
- Warm-water soaking
- Overnight camping trips
Overview Green Valley Campground is located near Arrowbear in the San Bernardino National Forest in Southern California. It is centered between Lake Arrowhead and Big Bear Lake, providing ample recreational opportunities in the area's pine-covered mountains. Green Valley Lake, known for its exceptional trout fishing, is located about a mile from this beautiful mountain campground.Recreation Green Valley Lake, which is known for its trout fishing, is located just minutes away. Boating and swim...