Warner Hot Spring
Warner Hot Springs reaches 138°F in the mountains northeast of San Diego, among California's hottest documented springs. Sitting at 3,170 feet with a sodium-sulfate composition of 355 mg/L TDS, it represents significant geothermal potential just 11 feet from the road.
The spring emerges near the Pacific Crest Trail in terrain where coastal maritime influence meets desert climate patterns. At a roadside location near Julian, it flows through chaparral vegetation with manzanita and chamise typical of the southern California backcountry, creating a surprising thermal contrast in mountain terrain.
Waters here are heated by circulation through deep faults in the Peninsular Ranges geology, where Precambrian crystalline basement rocks and younger plutonic intrusions provide the heat source. The sodium-sulfate signature indicates long residence time at depth, where thermal alteration of silicate minerals enriches the water chemistry.
The spring sits practically at road level with just 11 feet of access, making it among California's most convenient geothermal destinations. Indian Flats Campground, 7.7 km away, offers basic camping near the Pacific Crest Trail, though it closes seasonally for Arroyo toad breeding protection.
Is Warner Hot Spring worth visiting?
Best for
- Hot spring soaking
- Easy day trips
- Overnight camping trips
The water at Warner Hot Spring is slightly acidic (pH 6.6) with 355 mg/L total dissolved solids.
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17 sites. Pacific Crest Trail Access. No Water. The nearest water can be found at the Warner Springs Gas Station. Indian Flats will be temporarily closed for Arroyo Toad protection during breeding season beginning April 1st through at least May 31st.