Both inflatable spas in our catalog, the SaluSpa Hot Springs AirJet and the Coleman SaluSpa, list a top temperature of 104°F. When the dial stops there, it’s easy to read the maximum as the recommended setting.
This article explains where that number comes from and what the sources say about lower settings. It sits under our overview of hot tub benefits. It is general information, not medical advice.
Short answer: 104°F is a ceiling, not a target. The Consumer Product Safety Commission says hot tub water should never exceed 104°F, calls 100°F safe for a healthy adult, and says pregnant women should stick to 100°F. Thermostats can be off by up to 4°F, so check with a thermometer.
Where the 104°F limit comes from
In a release dated December 31, 1979, the CPSC said: “Hot tub water temperatures should never exceed 104 degrees Fahrenheit.” It reported 10 hot tub deaths recorded that year.
The same release said soaking at 106°F can bring on heat stroke, and that 100°F is “considered safe for a healthy adult.” CPSC repeated the limit in 1996: “Keep the temperature of the water in the spa at 104 degrees Fahrenheit or below.”
Cleveland Clinic’s 2025 guidance agrees: keep the water below 104°F.
The figures side by side
| Water temperature | What the sources say |
|---|---|
| 100°F (37.8°C) | Safe for a healthy adult; the maximum in pregnancy (CPSC, 1979) |
| 102°F (38.9°C) | Above this, possible fetal damage in the first 3 months (CPSC, 1979) |
| 104°F (40°C) | Never exceed (CPSC, 1979 and 1996); stay below (Cleveland Clinic, 2025) |
| 106°F (41.1°C) | Can bring on heat stroke (CPSC, 1979) |
The Celsius conversions are our arithmetic.
Your thermostat may be wrong
Here’s what the spec sheet won’t tell you. CPSC warned that hot tub thermostats “may err” by as much as 4°F. By that margin, a tub set to 104°F could be at 106°F or more, the temperature CPSC links to heat stroke.
CPSC’s advice is to check the water with an accurate thermometer before you get in. A floating one like the TempPro TempAir is rated ±0.9°F from 32 to 140°F, and it sends the reading to a display indoors. The listing is on Amazon, which sets the price.
Who should run it cooler
- Pregnancy: CPSC says to stick to the 100°F maximum. Cleveland Clinic goes further and says to avoid hot tubs.
- Alcohol or drowsy-making medicines: CPSC says drinking raises the drowning risk and that people taking medicines that cause drowsiness should not use hot tubs.
- Children: Cleveland Clinic says children under 5 shouldn’t use hot tubs, and older children should limit their time.
What about the temperatures in sleep studies?
A 2019 meta-analysis on warm baths and sleep used water at 40 to 42.5°C, which is 104 to 108.5°F. Those were baths and showers in studies, not hot tubs, and the top of that range is above CPSC’s ceiling. Don’t read it as permission to run a spa hotter.
My rule of thumb: pick the lowest setting you enjoy, and treat the dial’s 104°F as the most the water should ever read on your own thermometer.
Bottom line: keep a hot tub at or below 104°F, closer to 100°F if you’re pregnant, and trust a thermometer over the control panel. For the other health claims, see the hot tub benefits overview linked above.
Sources
- U.S. Consumer Product Safety Commission, “CPSC Warns Of Hot Tub Temperatures,” release 79-071, December 31, 1979: cpsc.gov
- U.S. Consumer Product Safety Commission, “CPSC Issues Warning for Pools, Spas and Hot Tubs,” release 96-139, June 3, 1996: cpsc.gov
- Cleveland Clinic, “Soak It In: How Hot Tubs Can Boost Your Health,” November 17, 2025: health.clevelandclinic.org
- Haghayegh S, et al., “Before-bedtime passive body heating by warm shower or bath to improve sleep,” Sleep Medicine Reviews, 2019 (abstract): pubmed.ncbi.nlm.nih.gov
- TempPro TempAir listing on Amazon, checked October 19, 2026