The wet-bulb temperature is a type of temperature measurement that reflects the physical properties of a system with a mixture of a gas and a vapor, usually air and water vapor. Wet bulb temperature is the lowest temperature that can be reached by the evaporation of water only. It is the temperature one feels when one's skin is wet and is exposed to moving air. Unlike dry bulb temperature, wet bulb temperature is an indication of the amount of moisture in the air. Wet-bulb temperature can have several technical meanings:

• Thermodynamic wet-bulb temperature: the temperature a volume of air would have if cooled adiabatically to saturation at constant pressure by evaporation of water into it, all latent heat being supplied by the volume of air.
• The temperature read from a wet bulb thermometer
• Adiabatic wet-bulb temperature: the temperature a volume of air would have if cooled adiabatically to saturation (along a dry adiabat) and then compressed adiabatically to the original pressure in a moist-adiabatic process (AMS Glossary).