Ultraviolet (UV) Radiation is part of the invisible spectrum of light that reaches the Earth from the Sun. Although the Earth's atmosphere protects us from the bulk of these rays, those that get through are still harmful, causing sunburn, skin cancer, skin wrinkling and aging, cataracts and other ocular damage. UV radiation can vary quite a bit over short distances and change dramatically during the course of a day. AccuWeather.com provides the only local UV Index that gives the current and forecast UV for each hour, rather than just a high for the day. This detail allows you to better plan your day to take advantage of the hours when UV is low for outdoor activities, and to use sufficient protection in hours when it is higher. The UV Index ranges from 0 (minimum levels) to 10 or more (very high levels). The stronger the sun, the higher the UV Index number, indicating a greater need for eye and skin protection.