Clouds Don't Block UV

Cloudy weather can feel safer than direct sunshine. The air may feel cooler, the sky may look softer, and the sun may be hidden from view. But that does not mean UV exposure disappears.

Ultraviolet radiation is invisible. You cannot feel it the way you feel heat, and you cannot always judge it by how bright or sunny the day looks.

Why This Matters

Many people skip sun protection when the sky is cloudy. That can lead to unexpected sunburn and unnecessary UV exposure during hiking, walking, running, cycling, golf, tennis, beach days, and outdoor work.

The American Academy of Dermatology also reminds people that skin is exposed to UV rays whenever they go outside, including on cloudy days and in winter.

What to Do Before You Go Outside

Check the UV Index before heading outdoors. If the UV Index is elevated, use layered protection:

• Wear broad-spectrum sunscreen.
• Use protective clothing where possible.
• Wear a wide-brim hat.
• Wear UV-blocking sunglasses.
• Seek shade, especially during stronger UV hours.
• Reapply sunscreen when outdoors for longer periods.

Frequently Asked Questions

Can UV rays go through clouds?

Yes. According to the EPA's UV Index guidance, up to 80% of solar UV radiation can penetrate light cloud cover, so a cloudy sky does not mean UV exposure has stopped.

Do clouds block UV rays completely?

No. Clouds reduce UV to some degree, but even under heavier cloud cover, meaningful UV exposure continues — clouds reduce UV, they do not remove it.

Is UV exposure a problem on cloudy days?

Yes. The American Academy of Dermatology notes that skin is exposed to UV rays whenever you go outside, including on cloudy days and in winter.

How much UV gets through clouds?

Up to 80% of solar UV radiation can pass through light cloud cover, per the EPA's UV Index guidance. Heavier cloud cover reduces UV further but does not block it entirely.