Most people check temperature and rain. UV is a different meter. A cool, bright morning can still sit at Moderate or High. This is the routine we built the homepage for.

Three numbers, not one

1. Current UV index — approximate open-sky intensity near the location we detected.
2. Today’s peak — the high for the day, with an approximate time. If that peak is 6 or above, treat late morning through mid-afternoon as a protection window even if 8 a.m. still looks mild.
3. Next few hours — cloud can drop UV and then give it back. A single snapshot is how people get caught.

Bands follow WHO / EPA: protect from 3 up; Very High and Extreme (8+) means minutes, not hours, of bare skin.

Match the kit to the band

• 0–2: Short errands are usually fine. Sunglasses still help in open glare.
• 3–5: Shirt, hat, SPF 30+ if you will be out more than a walk. See what UV index requires sunscreen.
• 6–7: Shorter unprotected stretches. Reapply if you sweat.
• 8+: Shade plus clothing plus sunscreen. Do not pick one.

Skin type, medicines, and altitude change how aggressive you should be. The SPF calculator turns skin type plus an index into a planning number. When unsure, protect more.

Then name the ground

The index is an open-sky rate. Dose goes up on sand, water, snow, and at elevation. A patio over pale concrete is not a park lawn. More on bounce: shade does not cancel UV. More on height: altitude raises UV. Side windows leak UVA even when you are “inside”: car glass.

Recheck when the sky changes

If you are at a kids’ game, a long run, or a job with outdoor breaks, glance at the next few hours before you decide “no sunscreen today.” Thin cloud that still throws a shadow can even raise UV for a bit—broken clouds.

Sources

WHO and EPA UV-index bands linked above. This page is how we intend the live tool to be used. Readings are estimates for sun-safety planning, not a clinic visit. FAQ-style chemistry and SPF answers: Guide.