UV index explained, when sunscreen really matters

The numbers

• 0 to 2 (Low). Sunscreen optional unless you're out for hours. Most winter days.
• 3 to 5 (Moderate). SPF 30 if you're outside for more than 30 minutes. A hat helps.
• 6 to 7 (High). SPF 30 minimum, hat, sunglasses, seek shade between 11 and 3.
• 8 to 10 (Very high). SPF 50, cover up, avoid 11 to 3 if you can. Skin burns in under 25 minutes.
• 11 and up (Extreme). Stay inside at peak hours. Skin can burn in 15 minutes.

What the SPF number really tells you

SPF 15 blocks 93% of UVB. SPF 30 blocks 97%. SPF 50 blocks 98%. SPF 100 blocks 99%.

The jump from 30 to 50 is small but worth it if you have fair skin or you're outside in strong UV. Don't pay extra for SPF 70+ thinking it's miles better. It isn't.

Reapplication matters more than the number

Most people apply too thin a layer and never reapply. The rule of thumb:

• A teaspoon for the face
• A tablespoon for each arm or leg
• A shot glass for the whole body

Reapply every two hours, and after swimming or sweating.

Mineral vs chemical sunscreen

Mineral (zinc, titanium): Works straight away, gentler on sensitive skin, doesn't sting eyes. Slight white cast.

Chemical (avobenzone, octocrylene): Lighter feel, invisible. Needs 20 minutes to absorb before sun exposure. Can irritate sensitive skin.

Cloudy days are sneaky

Up to 80% of UV passes through light cloud. Snow, sand, and water reflect UV back at you, adding 25 to 80% extra exposure. A cloudy day at the beach has burned more people than a sunny day in the city.

Today's UV

Open Window Today's UV card pulls live UV index data and tells you what protection level you actually need.

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