It says ultraviolet radiation from the sun can reach you on cloudy days, as well as bright and sunny ones.

VOA: special.2010.07.06

Oh, the weather's a lot better than New York. It's usually bright and sunny.

我家乡的气候比纽约好很多，那里总是阳光灿烂。

纽约和洛杉矶不一样 - SpeakingMax英语口语达人