Can you get sunburned on a cloudy day?
Yes, easily. Light cloud cover lets through up to 80% of UV, and scattered, broken clouds can briefly push UV above clear-sky levels by reflecting extra radiation down at you. Cloudy-day sunburn is common precisely because the warning signs — heat and glare — are missing.
Why clouds fool people
- UV isn't heat. Your skin senses infrared (warmth), not ultraviolet. A cool, grey 20°C day can carry the same UV as a scorching one — the temperature tells you nothing.
- Thin vs. thick matters. High, thin cirrus barely attenuates UV. Only dark, heavy overcast (the kind about to rain) blocks most of it.
- The broken-cloud effect. When the sun is out between cumulus clouds, the cloud edges scatter additional UV toward the ground — measurements show up to 25% more than a cloudless sky. The riskiest sky is sunny-with-clouds, not clear.
- Classic victim profile: hikers, boaters, and beachgoers on overcast days who skipped sunscreen "because there's no sun." Some of the worst burns happen at UV 6 under a white sky.
The fix is checking the number, not the sky: see the actual UV index at your location right now — it already accounts for today's cloud cover.