Home / Home / Do clouds block UV rays?Home clouds don block raysDo clouds block UV rays?No. Up to 80% of UV radiation penetrates cloud cover, so you can still burn on an overcast day. Clouds block visible light, not ultraviolet. If you’re outside for more than 15 minutes, wear SPF 30. Search Amazon As an Amazon Associate I earn from qualifying purchases.Related NotesExploreExploreExplorePrevious Do coated mousepads lose their effectiveness over time?Next Do car windows protect your skin from the sun?