What's the Best Hot Tub Temperature?
When I was younger, the target temperature for hot tubs was 105°F, but that's changed. Now the CPSC recommends temperatures no higher than 104°F. They also caution that one should always check the thermometer before entering a spa, and be aware that thermometers can be incorrect!
So, 104°F for the regular hot tub soak - but that comes with a disclaimer. High temperatures over 100°F are NOT recommended for pregnant women, hypertensive persons (with high blood pressure), or those with heart disease.
High temperatures can also irritate certain skin conditions, and temperatures of over 100°F are not recommended for children, who overheat more easily than adults.
But what about all those other spa activities, besides a spine-tingling hot soak? There are other recommended temperatures, depending on the use of the spa, hot tub or whirlpool.
Exercise
Exercises such as Yoga, or various types of core workouts or stretching, can be exhausting in a hot spa. If you use your spa for exercise, especially active exercise, you'll find a temperature below 90°F to be more comfortable. It's also safer, to prevent overheating and hyperthermia.
Therapy
For conditions such as arthritis, fibromyalgia and other chronic pain diseases, warmer water increases circulation to the joints and allows for a more comfortable therapeutic exercises. Also helpful for rehabilitative movements or therapies. For most warm water therapy, a temperature below the body temperature 98.6°F is desirable, something between 92°F–94°F.
Special Conditions
Children, obese persons and those with MS can overheat easily, and should not exceed 100°F in a spa or hot tub. In addition, it's important to limit your spa session time to 15–20 minutes, and take in non-alcoholic beverages to cool the body.
Pregnant women should take care not to exceed 92°F in the spa or hot tub, and take in plenty of water or juice before and after hot tubing, according to the Aquatic Therapy & Rehab Institute.
Those recovering from accidents or stroke can use a warm spa to slowly regain movements, by practicing simple flexion and extension exercises. Every patient may prefer a different temperature, but most will fall between 88°F–92°F.
Air Temperature
Also a factor in how hot or warm the water feels is the air temperature outside. An air temperature of 75°F may feel nice walking around outside, but can feel chilly as one sits in water that is below body temperature. 88°F may be perfect when the air temperature is above 80°F, but feel too cold when air temps are just above 60°F.