The UV Index Scale, Explained Level by Level

The UV index sorts the sun's strength into five bands, from Low to Extreme. Here is exactly what each level means and what to do about it.

Low: UV 0 to 2

The safest band. This is the reading you see early in the morning, late in the day, and through much of winter in northern states. You can spend time outside without much thought. People with very fair skin may still want sunglasses on bright days.

Moderate: UV 3 to 5

This is where protection starts to matter. UV 3 is the tipping point health bodies use as the cue to put on sunscreen. Wear SPF 30 or higher on exposed skin, add a hat and sunglasses, and take shade during the middle of the day. Most spring and fall afternoons across the US land here.

High: UV 6 to 7

Now the sun can do real damage in a short time. Unprotected fair skin may start to burn within 30 minutes or so. Cut back on direct sun between 10 a.m. and 4 p.m., reapply sunscreen every two hours, and cover up when you can. Typical of summer midday in much of the country.

Very High: UV 8 to 10

Burns come quickly here, sometimes in 15 to 20 minutes on fair skin. Treat midday sun with caution: stay in shade, wear a wide-brim hat and UV-blocking sunglasses, and keep sunscreen topped up. Common in southern states and at altitude in summer.

Extreme: UV 11 and above

The strongest band, seen in the desert Southwest, at high elevation, and in the tropics. Unprotected skin can burn in minutes. Avoid the sun in the middle of the day if you can, and use full protection when you are out: shade, cover, hat, sunglasses, and SPF 50+.

A quick note on burn times

Burn-time estimates are rough. Your real risk depends on your skin type, reflection from water or snow, altitude, and how much skin is exposed. Use the bands as a guide, not a stopwatch. When in doubt, protect more, not less.