The wet-bulb globe temperature (WBGT) is a type of apparent temperature used to estimate the effect of temperature, humidity, wind speed (wind chill), and visible and infrared radiation (usually sunlight) on humans. It is used by industrial hygienists, athletes, sporting events and the military to determine appropriate exposure levels to high temperatures. It is derived from the following formula: where Indoors, or when solar radiation is negligible, the following formula is often used: