Sunscreen Timer

Do you need sunscreen on a cloudy day?

The fastest sunburns of the year happen on overcast days. People look up, see grey, and skip the sunscreen — while ultraviolet light blasts right through the cloud layer onto unprotected skin.

Want a personalized reapply schedule based on your location and skin? Use the smart sunscreen timer →

Clouds barely block UV

Light cloud cover blocks only about 10% of UV. Thick cloud cover blocks around 50%. Even a fully overcast sky still lets 30 to 80 percent of UV through, depending on the cloud type. Cumulonimbus storm clouds offer the most shielding; high cirrus clouds offer almost none.

Why the UV index doesn't drop as much as it feels

On a cloudy June day, the UV index might read 6 or 7 even though the sky looks dim. That's still High territory. The smart sunscreen timer pulls the live UV value rather than guessing from cloud cover, which is why your reapply window can come up shorter than the dim sky suggests.

The 'edge of the cloud' effect

When the sun briefly breaks through a gap in the clouds, UV can actually spike higher than on a clear day — clouds at the edges of the gap reflect UV back down. Photographers know this as 'broken cloud' light. Skiers and sailors get burned this way constantly.

Don't downgrade the timer for clouds

Keep the activity setting honest — Light outdoor or Beach, whatever you're actually doing. The UV multiplier will adjust based on the real measured UV, not the visual sky. Cloudy days are when most adults make their worst sunscreen decisions; don't be one of them.

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