ozone layer shields the Earth from harmful ultraviolet (UV) radiation. Ozone depletion, as well as seasonal and weather variations, cause different amounts of UV radiation to reach the Earth at any given time. The UV Index, developed by the National Weather Service and EPA, indicates the strength of solar UV radiation on a scale from 1 (low) to 11+ (extremely high).

Every day the National Weather Service calculates the predicted UV Index for the next day in each area of the U.S. This UV Index forecast is published in mid-afternoon (Eastern time zone) at the EPA Web site. If the level of solar UV radiation is predicted to be unusually high, and consequently the risk of overexposure is greater than normal, the forecast includes a UV Alert. (You can sign up below to receive e-mail notification of UV Alerts for your community.)


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