DemacLenko WBTCalculator app for iPhone and iPad

The wet-bulb temperature is the temperature a parcel of air would have if it were cooled to saturation by the evaporation of water into it.

Wet-bulb temperature is largely determined by both actual air temperature and the amount of humidity in the air. At 100% relative humidity, the wet-bulb temperature equals the dry-bulb temperature, with lower humidity it is lower than the dry-bulb temperature.

A snowgun works using wet bulb temperature as main reference, because with low humidity in the air the snow production is more efficient and it can start with higher dry-bulb temperature.