The amount of UV light hitting Earth each day is measured and reported as the UV index. In the United States, the amount of ultraviolet (UV) light is measured in fifty different places, one in each of the fifty states. The highest intensity of UV light is given the equivalent UV index number 15 and the lowest amount is represented as 1. Using the numbers 1-15 weather services rate the amount of UV light present on any particular day. TV and radio stations report the UV index with the daily weather forecast in most countries.

If your local tv station weatherman were to announce on the television that the UV index was in the range of 3-4 today would you know what he meant? Using this chart you can easily look up the 15 different levels in the UV index. When we say unprotected we mean unprotected by sunscreen. Getting in the shade will help however your risk from UV light on a cloudy day remains high. You can get a sunburn on a cloudy day and UV light penetrates the clouds.