UV index: what it means and how to protect yourself
The UV index measures the intensity of the sun's ultraviolet radiation at a place and time. The higher it is, the faster it can damage skin and eyes. This guide explains each level and how to use the number. It is general information and does not replace the advice of a health professional.
The levels
- 0 to 2, low: minimal risk for most people.
- 3 to 5, moderate: protection is advisable, especially if you will spend a long time in the sun.
- 6 to 7, high: skin can be damaged fairly quickly; protection is necessary.
- 8 to 10, very high: damage can occur in a few minutes; take extra care.
- 11 or more, extreme: avoid direct exposure during the middle of the day.
What it depends on
- The height of the sun: it is stronger at midday and in summer.
- Altitude: it is more intense in the mountains because there is less atmosphere to filter the radiation.
- Clouds: they reduce radiation, but not always completely; with partly cloudy skies it can even rise for moments.
- Reflection: snow, sand and water reflect part of the radiation and increase exposure.
How to protect yourself
- From an index of 3, use broad-spectrum sunscreen and reapply it every few hours and after getting wet.
- Avoid direct sun during the middle of the day, roughly between 10 am and 4 pm.
- Wear a hat, UV-filtering sunglasses and clothing that covers the skin.
- Look for shade and take special care of children, whose skin is more sensitive.
How to see it on this site
On each city's Air and sun page you will find the expected maximum UV for today and its level. It is a model estimate and may differ from local measurements. If you have a skin condition or doubts about how to protect yourself, consult a health professional.
General, educational information: it does not replace professional advice or official warnings.