Unnamed Thermal Spring
Mount Diablo State Park shelters this 70-degree thermal spring in warm, dry foothills just 17 meters from a paved road. The 10.7-degree temperature rise above ambient creates noticeable warmth in a landscape of grass-covered hills and scattered oak woodlands.
Emerging at 665 feet elevation near Clayton, the spring flows within one of the Bay Area's most visited state parks. Rolling golden grasslands and dark oak thickets dominate the terrain. The water feels pleasantly warm as it emerges from earth, accessible via a quick walk from the parking area through typical foothill brush.
Access is excellent year-round. The spring lies within Mount Diablo State Park at a roadside location requiring minimal hiking. Spring and fall offer the most comfortable temperatures for visiting. Bring sun protection for the exposed grassland setting.
Mount Diablo's thermal springs result from heat rising along fault lines that also built this distinctive peak. The mountain itself has served as a navigational landmark for centuries, visible from much of the Bay Area and named by Spanish explorers for its prominent silhouette.
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