The UV Index, which was developed by the National Weather Service (NWS) and the U.S. Environmental Protection Agency (EPA), provides important information to help you plan your outdoor activities to prevent overexposure to the sun's rays. The UV Index provides an indicator of the expected risk of overexposure to the sun. The Index measures UV intensity levels on a scale of 1 to 11+, where low indicates a minimal risk of overexposure and 11+ means an extreme risk. The UV Index does not take into account clouds and other local conditions that affect the amount of UV radiation reaching the ground.