The UV index is an international standard measurement of how strong the ultraviolet (UV) radiation from the sun is at a particular place on a particular day. It is a scale primarily used in daily forecasts aimed at the general public. Its purpose is to help people to effectively protect themselves from UV light, of which excessive exposure causes sunburns, eye damage such as cataracts, skin aging, and skin cancer (see the section health effects of ultraviolet light). Public-health organizations recommend that people protect themselves (for example, by applying sunscreen to the skin and wearing a hat) when the UV index is 3 or higher; see the table below for complete recommendations.
|UV Index||Description||Recommended Protection|
|0–2||No danger to the average person||Wear sunglasses on bright days; use sunscreen if there is snow on the ground, which reflects UV radiation, or if you have particularly fair skin.|
|3–5||Little risk of harm from unprotected sun exposure||Wear sunglasses and use sunscreen, cover the body with clothing and a hat, and seek shade around midday when the sun is most intense.|
|6–7||High risk of harm from unprotected sun exposure||Wear sunglasses and use sunscreen having a sun protection factor of 15 or higher, cover the body with sun protective clothing and a wide-brim hat, and reduce time in the sun from two hours before to three hours after solar noon (roughly 10:00 AM to 4:00 PM during summer in zones that observe daylight saving time.|
|8–10||Very high risk of harm from unprotected sun exposure||Wear sunscreen, a shirt, sunglasses, and a hat. Do not stay out in the sun for too long.|
|11+||Extreme risk of harm from unprotected sun exposure||Take all precautions, including: wear sunglasses and use sunscreen, cover the body with a long-sleeve shirt and pants>, wear a very broad hat, and avoid the sun from two hours before to three hours after solar noon.|