You can still be affected by UV rays on cloudy days.

Cloud cover can only weaken some UV rays and cannot completely block them. In particular, UVA, which has strong penetration, can still pass through clouds. Additionally, UV rays can be reflected or scattered by the edges of clouds or the surrounding environment, so you can still accumulate UV exposure on cloudy days. Even on cloudy days, if you are outdoors for a long time, you should take sun protection measures, such as applying sunscreen, wearing a hat, or wearing UV-protective clothing.