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The UV Index Explained

Tap a range to see what it means.

What the UV Index Measures

An internationally standardized scale, developed by the World Health Organization, that measures the strength of ultraviolet radiation from the sun at a given place and time, helping people gauge their skin damage risk.

Low (1-2)

Minimal risk for the average person β€” no special sun protection precautions are generally necessary, though people with very sensitive skin may still wish to take basic precautions.

Moderate (3-5)

Some risk of harm from unprotected sun exposure β€” seeking shade during midday hours and wearing sun protection is generally recommended, especially for extended time outdoors.

High (6-7)

Significant risk of skin damage from unprotected exposure β€” protective measures like sunscreen, sunglasses, and protective clothing are generally strongly recommended during peak sun hours.

Very High (8-10)

High risk of harm from unprotected sun exposure, with skin damage able to occur relatively quickly β€” extra precautions are generally recommended, including limiting midday outdoor exposure when possible.

Extreme (11+)

The highest risk category, where unprotected skin can burn in a very short time β€” taking all available precautions is generally strongly recommended, including avoiding outdoor sun exposure during peak hours.

Why the UV Index isn't the same as temperature or cloud cover

This page is for general information only and is not a substitute for professional medical advice. A common misconception is that UV risk is closely tied to how hot or sunny a day feels, but UV radiation can be intense even on cool or overcast days, since clouds only partially block UV rays, which is why checking the actual UV Index rather than relying on how the weather feels is generally recommended.

Frequently Asked Questions

Can I get sunburned on a cloudy day?

Yes β€” clouds typically only block a portion of UV radiation, so a meaningful UV Index reading can still exist on an overcast day, meaning sunburn risk doesn't disappear just because the sun isn't visibly shining.

Does the UV Index change throughout the day?

Yes β€” UV Index levels are generally highest during midday hours when the sun is most directly overhead, and lower in the early morning and evening, which is why sun protection is often emphasized most strongly during that midday window.