The UV Index in Fall: Lower, but Not Zero
Why the number still matters in October.
The UV Index scale runs from 1-2 (low) to 11+ (extreme); protection is advised above 3.
Roughly 95% of the UV reaching Earth's surface is longer-wavelength UVA.
Questions we get a lot
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.
What does the UV index mean and when should I protect my skin?
The UV Index, from the EPA and WHO, rates the strength of midday UV on a scale from 1–2 (low) to 11+ (extreme). Dermatologists generally advise sun protection whenever it reaches 3 or higher. It appears in most weather apps and rises with sun elevation, altitude and proximity to the equator.
Is visible light bad for skin?
Visible light makes up about 45% of sunlight. Research shows high-energy visible (blue) light can worsen pigmentation and melasma, especially in medium-to-deep skin tones. Tinted sunscreens containing iron oxides help shield against it, which clear sunscreens generally do not.
r/AsianBeauty: 'Why do K-beauty sunscreens talk about UVA so much more than US ones?'
