UV Index Forecast UK

The UV index in the UK rarely reaches extreme levels thanks to its maritime climate, but readings can climb to 7 or 8 on clear summer days in southern England. Check the live forecast above for today’s peak UV and plan sun protection accordingly.

What is the UV index and how is it measured?

The UV index is an international standard that measures the strength of ultraviolet radiation from the sun. The UV index scale runs from 0 (low) to 11+ (extreme). In the UK the Met Office calculates the index using a combination of satellite data, ozone levels, cloud cover, and surface reflectivity. A reading of 1–2 is low, 3–5 moderate, 6–7 high, 8–10 very high, and 11+ extreme. The scale is linear: a UV index of 6 delivers roughly twice the skin-damaging radiation as a reading of 3.

UV index today UK – what to expect

The live conditions above show the current UV index today UK for your location. Readings typically peak between 11am and 3pm BST, even when cloud cover is broken. In London, for example, a sunny May afternoon can produce a UV index today London of 5 or 6. The Met Office UV index weather forecasts are updated daily and you can use the widget to see how the index changes through the day. On overcast days the UV index is generally 30–50% lower than on clear skies, but UVA rays still penetrate cloud, so protection remains important.

When is UV highest in the UK?

The UK UV index by month follows the sun’s elevation. Index values are negligible from November to February (0–1). They start rising in March (index 2–3) and peak between May and August, when southern England and Wales regularly see index 6–7 and occasionally 8. Scotland and Northern Ireland are typically one to two points lower because of higher latitude and more persistent cloud. The highest UV index in the UK ever recorded at a Met Office station is 9.3, measured at Camborne, Cornwall, on 25 June 2024.

UV index scale explained – when do you need protection?

The UV index scale is divided into risk bands. At index 0–2 no protection is needed for normal daytime activity. At 3–5 the NHS advises seeking shade around midday, wearing a sun hat and sunglasses, and applying SPF 30+ sunscreen. At 6–7 these measures become essential; skin can burn in under 20 minutes. Index 8+ is rare in the UK but can occur during heatwaves – see our UK Heatwave & Hot Weather guide for more. The Met Office issues a UV alert when the index is forecast to reach 6 or higher, and you can find official updates on the UK weather hub.

Does cloud cover or altitude affect the UV index?

Thick cloud can reduce UV by 50–90%, but thin or broken cloud offers only modest protection. Reflective surfaces such as snow and water can amplify UV exposure. Altitude matters too: the UK’s highest peaks, such as Ben Nevis, can see a UV index 10–20% higher than at sea level. Always check the UV index Met Office forecast before heading to the hills – the combination of reflection from snow and thinner air can catch walkers out even in spring.

Frequently asked questions about the UV index

For the latest daily readings and a detailed outlook, see our 10-day forecast page, which includes UV index projections for the week ahead.