Start using sunscreen when the UV index hits 3. That's the WHO's threshold—not because 3 feels intense, but because unprotected skin can take damage in as little as 30 minutes at that level, especially around midday.

A UV index of 3 often doesn't feel like a scorcher. You won't necessarily feel hot or uncomfortable. UVA is still reaching your skin and doing quiet, cumulative damage you won't notice until years later.

What to do at each level

0–2: Most people can skip sunscreen for short outings. Sunglasses and shade still help. If you burn easily, SPF 15+ won't hurt.

3–5: This is where sunscreen kicks in. Use broad-spectrum SPF 30 or higher, reapply every two hours, and limit time in direct sun between 10 a.m. and 4 p.m.

6–7: Same routine, but be more careful about midday exposure. Long sleeves and a hat help.

8+: Treat it seriously. Stay in shade during peak hours if you can. Unprotected skin can burn in minutes.

Pick the right sunscreen

Look for "broad-spectrum" on the label—that means it covers both UVA and UVB. SPF 30 blocks about 97% of UVB; SPF 50 blocks about 98%. No sunscreen blocks everything, and most people apply too little to get the full rating.

Use about a shot-glass amount for your whole body. Put it on 15–30 minutes before going out. Reapply every two hours, or sooner if you're swimming or sweating.

Clouds don't cancel the UV index

UV passes through cloud cover. Some of the worst sunburns happen on overcast days because people skip protection. Check the forecasted UV index, not just the sky.

Where you live matters too. At mid-latitudes, UV 3+ is common from spring through fall. Near the equator, it can hit that level year-round. Altitude and travel toward the tropics push it higher than you might expect.

Sunscreen isn't the whole story

Shade, UPF clothing, and a brimmed hat do more than sunscreen alone—and they don't wear off. If your shadow is shorter than you are, UV is near its peak. UV400 sunglasses protect your eyes; cheap tinted lenses without UV filtering can actually let in more damage by dilating your pupils.

Kids, fair skin, and anyone with a history of sunburns should be extra careful at UV 3 and above. This isn't medical advice—talk to a dermatologist if you have specific skin concerns.