Quick answer: UV radiation reaches your eyes year-round, not just on sunny summer days — it passes through clouds (up to 89% of UV can penetrate cloud cover) and reflects intensely off snow (up to 80%), nearly doubling your exposure in winter. UV400-rated sunglasses block essentially all UVA and UVB radiation, and wearing them consistently — not just in summer — is what actually protects against cumulative, largely irreversible eye damage.
The part most people get wrong: UV isn't a "hot weather" thing
UV exposure correlates with the sun's angle and reflection, not with air temperature. That's why a cold, bright winter day on snow can deliver more UV exposure to your eyes than a humid summer afternoon. Two specific numbers explain why:
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Snow reflects up to 80% of UV radiation back up toward your eyes, nearly doubling total exposure compared to the same sun without snow on the ground.
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Up to 89% of UV rays pass through cloud cover. A grey, overcast sky feels lower-risk, but it isn't — most of the UV radiation still reaches you.
Quick tip: if you only reach for sunglasses when it's sunny and warm, you're likely unprotected during exactly the conditions — snow, overcast bright days, high altitude — where UV exposure is often highest.
Why cumulative exposure is the real concern
UV damage to the eyes builds up over a lifetime rather than showing up after one bad day. A striking detail from eye-health research: most of a person's total lifetime UV exposure happens before age 18 — which is also why starting UV protection early, and keeping it consistent rather than seasonal, matters more than most people assume.
What that cumulative exposure can lead to
What "UV400" actually means, and why it's the number to look for
UV400-rated lenses absorb ultraviolet light up to the 400-nanometer wavelength, which covers essentially all UVA and UVB radiation that reaches the earth's surface. It's a pass/fail spec, not a spectrum — a lens is either rated UV400 (blocking effectively all harmful UV) or it isn't, regardless of how dark the tint looks. Darkness and UV protection are separate properties; a light-tinted UV400 lens protects your eyes just as well as a very dark one.
A simple rule for when to actually wear sunglasses
Daylight hours, essentially — not just "when it's sunny." That includes overcast days, winter, driving, and anywhere near snow or water where reflection adds to direct exposure. Every pair in our men's and women's collections is UV400-rated, so the protection question is already answered — the only decision left is style.
FAQ
Do I need sunglasses on cloudy days? Yes — up to 89% of UV radiation passes through cloud cover, so a grey sky doesn't meaningfully reduce your exposure the way it reduces visible brightness.
Is UV exposure worse in winter than summer? It can be, specifically around snow. Snow reflects up to 80% of UV rays, nearly doubling exposure compared to the same UV index without snow on the ground — which is why ski and snowboard communities take eye protection especially seriously.
Does a darker lens mean better UV protection? No. Tint darkness and UV protection are unrelated properties. Always check for a UV400 rating specifically rather than assuming a darker lens is safer — a dark lens without UV protection can actually be worse, since it causes your pupils to dilate and let in more UV.
