UV index

Solar UV index (UVI) is a measure of the intensity of UV radiation at the Earth's surface. The index is expressed as a value greater than zero, and higher, greater is the probability of cutaneous and ocular lesions and so it takes a short time to produce these lesions.

It is a daily forecast, calculated and issued 24 hours in advance, of the amount of UV radiation that receives the surface of the Earth during the time of greater solar lighting, which generally sits around a true noon (although not exactly matches the conventional hour 12:00).

This prediction is derived from the combination of five elements: 1) latitude, 2) day of the year, 3) total amount of ozone over the area, 4) elevation above the level of the sea, and 5) amount of cloud cover.

It has a scale of 0 to 20, it has categorized that exposure through five descriptors (e.g., minimal, low, moderate, high, very high), which is used to explain the intensity of each of the values. This index is useful to know how long you can be to the Sun depending on the skin type and the sunscreen that is used.

The reader then has a series of PDF documents that will help you learn more about this topic.