It certainly sounds like an obvious question but it regularly confuses new spa owners. Most spas control systems have a maximum of 40 degrees Celsius, however 40 degrees is not a recommended temperature to spa in.
Some Like it Hot, Hot, Hot!
The reason spas have a maximum temperature of 40 degrees is for safety reasons. Any outdoor spa that goes over this temperature is not fit for use. A recommended temperature setting for an outdoor spa pool is around 36-37 degrees Celsius (blood temperature); this is more comfortable and allows for a slight temperature drop whilst in the spa. You will find each individual will have a temperature preference and may come down to trialling different temperature settings.
Plunge Pools and Swim Spas
In the warmer months a spa temperature will most likely be too warm. Swimming temperature can be anywhere from 24 to 27 degrees. This really depends on the ambient temperature and what you prefer! Not only will you be able to cool off, but you’ll also be saving on heating costs!
Health Precautions
It is always important to consult your doctor if you are unsure whether hot water could potentially affect you. Pregnant women should avoid hot water as it can damage the foetus. People with heart conditions or extremely high blood pressure should be cautious of higher temperatures.
Article Source: Happy Hot Tubs