5 points
Dry bulb is a normal temperature reading with say a thermometer. Wet bulb is that same thermometer but it is wrapped in a wet cloth to simulate evaporation of sweat.
The purpose of wet bulb temperature measurement is to fix the dangerous temperature threshold at body temperature instead of having to adjust for humidity. So if the wet bulb temperature crosses 35C/95F you know that it is dangerous to even be outside because your sweat can’t even evaporate enough to prevent you from overheating just standing in the shade.