Healthy adults can safely soak in hot tubs for 15 to 20 minutes in appropriate water temperatures. The maximum safe water temperature for adults is 104 degrees Fahrenheit. If more time is desired in the hot tub, an individual may cool off during a break and re-enter the hot tub.
To ensure that the water temperature does not exceed 104 degrees Fahrenheit, the bather should keep a thermometer in the hot tub. Even within suggested temperature guides, pregnant women or individuals with heart disease, diabetes, high blood pressure or any other serious illness should not use a hot tub without first checking with a doctor.