Up to 80% of UV rays pass through clouds, so a heavily overcast day can still deliver enough UV to burn and to age skin.
Dermatologists warn that cloud cover gives a false sense of safety: most UV still gets through, and the aging UVA wavelengths stay nearly constant whether the sky is blue or gray.
Questions we get a lot
Is sunscreen necessary on cloudy days?
Yes. Up to 80% of UV rays pass through clouds, and UVA — the deeper-penetrating, aging wavelength — stays fairly constant regardless of cloud cover. A cool, overcast day can still deliver enough UV to damage skin, so daily broad-spectrum sunscreen is recommended.
How does UV light age and damage skin?
UVB is absorbed by DNA in surface cells, causing direct mutations that can lead to skin cancer. UVA penetrates deeper, generating free radicals that damage DNA, collagen and elastin — producing wrinkles, sagging and dark spots. The damage accumulates over a lifetime, so daily protection pays off even on gray days.
r/SkincareAddiction: 'I got sunburned on a cloudy day — how is that even possible?'