This is an experimental product.

The UV Alert product (see graphic below) is a joint venture between the NWS and the EPA to provide guidance for areas around the contiguous 48 states that are expected to experience well above normal UV radiation levels during the mid-day period. If you are within a UV Alert region extra precautions should be taken to protect oneself from the sun's UV radiation. The graphic below shows areas of 'near or below' climatological levels of UV radiation for that particular day (white), or areas expected to be 'above normal' UV conditions (yellow), and areas expected to be 'well above normal' conditions (red). The later areas are considered to be within a UV Alert region.

The UV Alert is based statistically upon a locale's daily climatological mean UV Index and its historical variability for that day (standard deviation). Initially, for a locale to qualify to be within a UV Alert region the UV Index must be "High" or 6 and above. If the UV Index is greater than the locale's climatological mean plus one half standard deviation it is considered to be 'above normal'. If the UV Index is greater than the locale's climatological mean plus one standard deviations it is considered to be 'well above normal' and placed within the UV Alert region.

Additional UV Index information are available on EPA Sun Safety web site