The scale · WHO standard
The ultraviolet rating, explained
Seen a UV rating of 7 in your weather app and wondered what it actually demands? The ultraviolet rating is the everyday name for the official UV index — a 0 to 11+ score of the sunburn-producing power of sunlight, defined by the WHO and identical worldwide. Here is what every rating means, when protection becomes essential, and where today’s rating stands for your location.
Rating, index, level — same thing?
Yes. Weather apps, TV forecasts and sunscreen packaging mix the words freely — UV rating, UV index, UV level — but they all point to one official scale. A rating of 7 in Phoenix means exactly the same skin risk as an index of 7 in Berlin. That is the whole point of the system: one number, one meaning, anywhere on Earth. If you prefer the formal write-up, the UV index scale guide covers the same bands in index language.
Weather apps sometimes label the same number the ultraviolet rating — different name, identical 0–11+ scale.
The rating bands, 0 to 11+
Three things people get wrong about the rating
First: it isn’t about temperature. The UV index measures radiation, not heat — a crisp 18°C June day regularly scores higher than a hot August afternoon. Second: clouds barely help. Up to 80% of UV passes through light cloud, so “overcast” does not mean “safe”. Third: the scale is open-ended. 11+ is a floor for “extreme”, not a ceiling — high-altitude and tropical locations regularly exceed it.
Frequently asked questions
What is an ultraviolet rating?
The ultraviolet rating — often shortened to UV rating — is the everyday name for the WHO’s UV index: a 0 to 11+ score of how strongly sunlight burns unprotected skin. The higher the rating, the faster the damage.
Is the ultraviolet rating the same as the UV index?
Yes — identical scale, identical numbers, different word. Forecasters and apps use rating, index and level interchangeably; a UV rating of 7 and a UV index of 7 describe exactly the same risk.
What is a safe ultraviolet rating?
Ratings of 0–2 are low risk for most skin types. From a rating of 3 the WHO recommends SPF 30+, and from 8 midday shade becomes essential. No rating above 0 is entirely risk-free for very fair skin during long exposure.
What ultraviolet rating can you tan at?
Skin tans — and burns — at any rating from about 3 upward. Dermatologists advise against deliberate tanning; if you do tan, ratings of 3–5 with SPF 30+ and short sessions carry the least risk.