What the UV index means, and when to cover up
How the UV index works, what each level means, and why 3 is the number to watch.
The short answer
The UV index is a number that tells you how strong the sun’s ultraviolet (UV) radiation is where you are. It starts at 0, and the higher it goes, the faster UV can damage your skin and eyes. When it reaches 3, both the World Health Organization (WHO) and ARPANSA, Australia’s radiation protection agency, advise sun protection.
One scale for every country
The Global Solar UV Index was developed by the WHO with the United Nations Environment Programme, the World Meteorological Organization and the International Commission on Non-Ionizing Radiation Protection. That is why a UV index of 8 means the same thing in Sydney, Singapore and London.
The five levels
| Level | UV index | What the WHO advises |
|---|---|---|
| Low | 0 to 2 | You can usually stay outside safely without protection. |
| Moderate | 3 to 5 | Seek shade around midday, and wear a shirt, sunscreen and a hat. |
| High | 6 to 7 | Seek shade around midday, and wear a shirt, sunscreen and a hat. |
| Very high | 8 to 10 | Avoid being outside around midday. A shirt, sunscreen and a hat are a must. |
| Extreme | 11 and above | Avoid being outside around midday. A shirt, sunscreen and a hat are a must. |
Levels from the WHO’s Global Solar UV Index guide. Advice from the WHO’s questions and answers on the UV index.
Why the middle of the day matters
UV changes through the day, so forecasts usually give the day’s highest value. That peak falls in the four hours around solar noon. Depending on where you are and whether daylight saving applies, solar noon falls between midday and 2 pm, so the strongest sun often comes later than people expect.
Why 3 is the number to watch
The WHO says that below a UV index of 3, even very fair skin is at limited risk under normal conditions. From 3 upwards, protection is needed, and the message gets stronger from 8. ARPANSA uses the same line and recommends five measures together when the index is 3 or above:
- sun-protective clothing that covers as much skin as possible
- broad-spectrum, water-resistant SPF50+ sunscreen, put on 20 minutes before you go outside and every two hours after
- a broad-brimmed or legionnaire-style hat
- shade
- sunglasses that meet the Australian Standard
Cool weather is not a guide
ARPANSA notes that Queensland, the Northern Territory and parts of New South Wales, South Australia and Western Australia still reach UV 3 or above throughout winter. UV also reflects off snow, and it is stronger at high altitude, so a cold day in the mountains can still call for cover.
Check it every morning
ARPANSA recommends checking the UV index every morning as part of your routine. Your national weather service publishes the day’s UV forecast each morning. Our UV and heat pages show how strong the sun gets in each month, for more than 100 cities.
The places sleeves miss
Long sleeves cover most of the arm, but the backs of the hands and the back of the neck are often left out. The Meriggio · Italian · say it “meh-REED-joh”The shady spot where you rest through the midday heat. (women’s fit, men’s fit) has hand covers in the cuffs and a neck shade in the collar for those two places.