2-in-1 style thermometer is ideal for spas and swimming pools:
Spa users, yellow caution area indicates temperatures in excess of 104° F / 40° C.
PLEASE NOTE - Your thermometer is printed with a yellow background at the 104°F / 40° C mark as a caution reminder. This temperature is the generally recommended limit to heat your spa water for healthful use. If you wish to heat your water above this limit, it is recommended you consult a physician for advice.