Hot spring temperatures: what's a soak and what's a hazard
Spring temperatures on this site come from survey records, and they range from cool trickles to water that will boil an egg. Here's how to read them — and why the number at the source isn't always the number in the pool.
The comfort bands
Below 80°F reads as cool to lukewarm — refreshing on a hot day, disappointing in October. The mid-80s through mid-90s is bath-warm and easy to stay in for a long time. Around 100–106°F is the classic hot-tub soak most people are after. Past 110°F, most bodies tap out in minutes.
Above 120°F, water stops being recreation. It causes burns with brief exposure, and springs at 150°F and up scald instantly. Some springs on this site are boiling at the source — they're listed because they're remarkable, not because you can get in.
Source temperature isn't pool temperature
The recorded number is usually the hottest measured point — often the vent itself. Pools cool as water spreads, mixes with creek flow, and sits in the air, which is why a spring recorded at 140°F can feed a soaking pool that's a perfect 103°F ten feet away.
That also cuts the other way: flow shifts, and a pool that was comfortable last month can run hotter after a dry spell concentrates the source. Test with a hand before anything else, every visit.
When the record says 'hot' or 'warm' instead of a number
Plenty of springs were documented by surveyors who classed them as warm, hot, or boiling without a thermometer reading. We show that class rather than inventing a number. Treat an unquantified 'hot' with the same respect as a triple-digit reading.
Heat is a drug — dose it
Hot water drops blood pressure and dehydrates you faster than you notice, especially at elevation, and alcohol multiplies both. Limit soaks to 15–20 minutes before cooling off, drink water, and get out slowly. Pregnant visitors and anyone with a heart condition should talk to a doctor before soaking at all.
Keep your head above water in any natural hot spring. Warm fresh water can host organisms you don't want near your nose or ears — it's a rare risk, but the prevention is free.