Hot spring temperature guide
Type a temperature from any listing or thermometer to see what it means for a soak.
Temperature bands at a glance
| Water | What it feels like | Typical soak |
|---|---|---|
| Below 80°F (27°C) | Cool to lukewarm, refreshing on a hot day | As long as you are comfortable |
| 80 to 97°F (27 to 36°C) | Warm, like a bath that has cooled | Long, relaxed soaks |
| 98 to 104°F (37 to 40°C) | Classic hot-tub heat | 10 to 20 minutes, then cool down |
| 105 to 112°F (41 to 44°C) | Very hot, many people cannot stay in | A few minutes at most |
| Above 112°F (44°C) | Too hot to enter; burns become possible | Do not enter |
Source temperature versus pool temperature
Most temperatures in this directory were measured where the water comes out of the ground. By the time it reaches a soaking pool it has usually cooled, sometimes by 20°F or more, or been mixed with creek or tap water. A spring listed at 140°F may still have a perfect 102°F pool downstream. The reverse is true too: a small pool right next to the source can be much hotter than the one you used last time.
Soaking safely
- Test the water with your hand or a thermometer before getting in, every time.
- Drink water before and after. Hot water makes you sweat more than you notice.
- Skip alcohol. It adds to dehydration and dizziness and is a factor in many hot water accidents.
- Stand up slowly. Blood pressure drops in hot water, and fainting on wet rocks is a real risk.
- Keep your head above the water at natural springs because of the rare amoeba Naegleria fowleri.
- Pregnant people, young children and anyone with heart conditions should get medical advice before soaking in very hot water.
This page is general information, not medical advice. Guidance based on the US Consumer Product Safety Commission's hot tub recommendations and CDC advice on recreational water.
Frequently asked questions
What is the best temperature for a hot spring soak?
Most people are comfortable between 98°F and 104°F (37°C to 40°C). 104°F is the upper limit the US Consumer Product Safety Commission recommends for hot tubs, and the same logic applies to natural pools.
How long should you stay in a hot spring?
In water around 104°F, 10 to 20 minutes at a time is a common guideline. Get out, cool down, drink water and go back in if you feel fine. In cooler water you can stay much longer.
Is it safe to soak in a hot spring when pregnant?
Health authorities advise pregnant people to avoid raising their core temperature, especially in the first trimester. Talk to your doctor or midwife before using hot springs or hot tubs.
What is 40°C in Fahrenheit?
40°C is 104°F. A quick way to convert is to multiply the Celsius figure by 1.8 and add 32.