A forecast that predicts the maximum level of UV tomorrow. Just like a weather forecast, the UV Index is designed to help people plan ahead; in this case, planning for protection against overexposure to the sun. The UV Index was first introduced in 1995 and is published on a daily basis in America by the EPA and the National Weather Service.

UV Index is a way of expressing the amount of sun-burning UV radiation. It was invented to inform the public about the intensity of UV radiation, and is now published in newspapers and on TV. The definition of the UV Index is the same throughout the world, so it's a great way to learn about the UV hazards at your travel destinations. The Index is a simple number. 1-3 means low exposure; 4-6 means medium; 7-9 means high; and more than 10 means extreme exposure. Mostly wavelengths in the UV-B contribute to the UV Index. The contribution from the UV-A is only about 10%. Therefore, the UV Index is highly affected by the thickness of the ozone layer, in contrast to UV-A radiation. The time you can stay outside in the sun at a given UV Index depends also on on your skin type. For example, if you have fair skin (skin type I) and the UV Index is seven, it takes less than 20 minutes until your skin starts to redden. If you have a dark skin color the same UV level may need more than 40 minutes to cause an effect. Check out the noontime UV Index at San Diego measured by the NSF network! During summer it is typically 10—this means extreme.

Describes the level of solar UV radiation at the Earth's surface. Educational tool to alert people about the need to adopt protective measures.