UV index in the UK: what the numbers mean
The UV index is a number, usually from 1 to 11 or more, that says how strong the sun’s ultraviolet radiation is at ground level. The higher the number, the faster unprotected skin is damaged. In the UK it matters from spring to early autumn, mostly in the middle of the day.
The scale
The Met Office uses these bands and advice in its forecast definitions:
| UV index | Exposure | Met Office advice |
|---|---|---|
| 1 to 2 | Low | No protection required. |
| 3 to 5 | Moderate | Seek shade during midday hours, cover up and wear sunscreen. |
| 6 to 7 | High | Seek shade during midday hours, cover up and wear sunscreen. |
| 8 to 10 | Very high | Avoid being outside during midday hours. Shirt, sunscreen and hat are essential. |
| 11 or over | Extreme | Avoid being outside during midday hours. Shirt, sunscreen and hat are essential. |
How high does it get in the UK?
Not as high as on holiday. The Met Office says the index does not exceed 8 in the UK, that 8 is rare, and that 7 occurs on exceptional days, mostly in the two weeks around the summer solstice in late June. Values of 9 and 10 are common around the Mediterranean.
The NHS says the sun in the UK is strongest between 11am and 3pm from March to October. Outside those months the index is usually low all day.
What UV index do you need to tan?
Skin tans and burns for the same reason: ultraviolet light is damaging it. The NHS advises protecting your skin when the UV index is 3 or higher, so 3 is the practical answer. Below that there is little UV to react to. At 3 and above, skin can tan, and it can burn.
The NHS is blunt about what that means: “There’s no safe or healthy way to get a tan.” A tan does not protect you from the sun’s harmful effects.
If you are going to be out in the sun anyway, the NHS advice is:
- Spend time in the shade between 11am and 3pm.
- Use sunscreen of at least SPF 30 with at least 4-star UVA protection.
- Cover up with clothing, a hat and sunglasses.
- Take extra care with children.
Common questions
Can you tan at UV 3? Yes, slowly, and you can also burn. It is the level at which the NHS says to consider protecting your skin.
Can you tan or burn when it is cloudy? Yes. The NHS says “you can burn in the UK, even when it’s cloudy.” Thin or broken cloud lets a lot of UV through.
Is UV high whenever it is sunny? No. A clear day in December can have a UV index of 1, because the sun is low in the sky. UV depends mainly on how high the sun is, so it peaks around the middle of the day in late spring and summer.
Is UV low whenever it is cool? No. UV has nothing to do with temperature. A breezy 15°C day in May can have a higher index than a hot evening in August.
What about vitamin D? The NHS says most people in the UK can make the vitamin D they need from sunlight from late March or early April to the end of September, and that between October and early March the sun is not strong enough. It suggests everyone consider a daily supplement in autumn and winter.
UV and sunshine are two different forecasts
The UV index tells you how strong the sun is. It does not tell you whether the sun will be out. For that you need a sunshine forecast: which hours will have clear sky and which will be cloud.
The two answer different questions, and you often want both. In June, the sunshine forecast tells you when it will be bright and the UV index tells you to take a hat. In January, UV is low all day and the only question is which hour, if any, will have sun worth going out for.
Sunny Hours answers the second question. It does not show a UV index, so check the Met Office or your phone’s weather app for that.
Last updated 8 October 2026.