Ultraviolet (UV) Index Scale – The UV index, which was developed by the National Weather Service (NWS) and Environmental Protection Agency (EPA), predicts the next day’s ultraviolet radiation levels on a scale of 1-11+ . The scale helps people decide about their behaviors to protect themselves from too much sun. Normally, the ozone layer shields the Earth from harmful Ultraviolet (UV) rays. The level of radiation that reaches the Earth varies depending on the amount of ozone depletion as well as variations in seasons and weather conditions.
The EPA issues a UV Alert when the level of solar UV radiation is predicted to be unusually high, and as a result, the risk of overexposure to UV rays is greater. The UV Index Scale is consistent with the scale used by the World Health Organization. The following table summarizes the UV levels.
UV (Utra Violet) Index Table
UV Level UV Meaning
2 or less Low risk
3, 4, and 5 Moderate risk
6 to 7 High risk from unprotected sun exposure. Therefore sunscreen should be used with a SPK (sun protective factor) of at least 15, and one should wear a wide brim hat and UV protective sunglasses
8 to 10 Very high risk of harm from unprotected sun exposure.
11 or higher Extreme risk of harm.
Information on protecting ones self from UV rays is provided in our Preventive Health Channel.