UV index explained — and what it means for sunscreen
The UV index is the World Health Organization's standard scale for how intense the sun's ultraviolet radiation is at a given place and time. It's a small number with big consequences for sunscreen timing.
Want a personalized reapply schedule based on your location and skin? Use the smart sunscreen timer →
The scale, level by level
UV 0–2 is Low. UV 3–5 is Moderate. UV 6–7 is High. UV 8–10 is Very High. UV 11 and above is Extreme. The smart sunscreen timer reads your live UV index from currentuvindex.com and shortens the reapply window automatically as the number climbs. Under UV 8, fair skin can reach a burning dose in under 25 minutes.
What drives the UV index up
Latitude (closer to the equator = higher), elevation (higher altitude = thinner atmosphere = more UV), time of day (10 a.m. to 4 p.m. is peak), season (summer in your hemisphere), cloud cover (light clouds barely reduce UV, heavy clouds can), and surface reflection (snow, sand, and water all amplify exposure). A cloudy ski day at altitude can deliver more UV than a sunny day at sea level.
How to use the live UV reading on this site
When you allow location access, the smart sunscreen timer fetches the current UV index for your exact coordinates and updates the calculation. You'll see the bucket (Low, Moderate, High, Very High, Extreme) right under the input. If you'd rather not share location, you can type the UV index manually — most weather apps and the iPhone weather widget show it.
When the UV index lies to you
UV index reports the highest expected level for the day, not the level at this exact minute. In early morning or late afternoon, the actual UV is much lower than the headline number. The smart timer uses the live point-in-time value from currentuvindex.com, so it's more accurate than what's on the morning forecast — but always trust visible signs (skin tingling, redness) over any number.
Related guides
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Read moreSunscreen at the Beach
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