The UV index forecasts the intensity of ultraviolet (UV) light for any given day. The index helps people know what precautions to take to avoid sunburn or other skin damage from being in the sun too long.
The UV index is listed on the weather page of many daily newspapers. Sun protection measures, such as wearing sunscreen, should always be taken when the UV index is 5 or above. The UV index is measured on a scale of 0 to 11+.
WebMD Medical Reference from Healthwise