The UV Index (UVI) is a measure of the strength of the sun's ultraviolet (UV) radiation at the Earth's surface. It helps you estimate how quickly unprotected skin can burn and what level of sun protection is appropriate.

What the numbers mean in practice

• UV 1–2: Most people can spend a fair amount of time outside without burning, though very fair skin can still be affected.
• UV 3: This is the point where sun protection becomes recommended for everyone.
• UV 6: Fair-skinned people may begin to burn in about 20–30 minutes without protection.
• UV 8: Sunburn can occur in around 15–20 minutes for fair skin.
• UV 11+: Burning may occur in under 10 minutes for some people.

These times vary significantly depending on:

• Your skin tone and how easily you burn.
• Altitude (higher elevations have stronger UV).
• Reflective surfaces like snow, sand, or water.
• Whether you're in direct sunlight or shade (shade reduces but doesn't eliminate UV exposure).

Common misconceptions

• Clouds don't block all UV. Up to 80% of UV radiation can pass through thin clouds.
• You can get sunburned when it's cool. UV depends on the sun's angle, not the air temperature.
• Winter isn't always safe. Snow can reflect UV and increase exposure.
• You may not feel UV. Unlike heat, UV radiation doesn't have a sensation, so skin damage can occur before you notice anything.

A simple rule to remember

• UV 0–2: Enjoy the outdoors.
• UV 3–5: Protect yourself if you'll be outside.
• UV 6+: Take sun protection seriously.
• UV 8+: Limit time in direct midday sun.
• UV 11+: Avoid unnecessary direct sun exposure during peak hours.

Additional links ⬇️

UV levels - Met Office

Sunburn - NHS

Sunscreen and sun safety - NHS

Published: Jul 7, 2026