UV index (UVI)

The UVI is a measure of the level of [sunburning] UV radiation.

The values of the index range from zero [to eleven and beyond] - the higher the UVI, the greater the potential for damage to the skin and eye, and the less time it takes for harm to occur.

The UVI is an important vehicle to alert people about the need to use sun protection.

Source: WHO UV Index 

UV Index

Ultraviolet radiation