Ideal Bath Water Temperature. Personal preference for the temperature of bath water is one major factor in deciding the levels that are ideal for the individual. Bath water temperature should be just a degree or two high than normal body temperature. However, for some people this may not be hot enough. It is important to realize that from about 39 degrees Celsius (102F) upwards, the temperature of the bath water can have a physiological effect on the body. Some of these effects can compromise a personâs health.