Uh weird, this is not supposed to happen. There is no setting in the weather effect to make the world become dark. This never happened to me or to anyone else that I know. I think it could be related to your pc maybe? Are you sure your GPU is not overheating, which could explain that kind of trouble?
Well I don't know. I'm taking your screenshots very seriously, so thanks for sharing them. I'll check everything in the game to try to discover if something's wrong. But it's really weird that it never happened to me or to anyone else who played.
Could you please edit your comment and delete the 2nd screenshot, as it gives the answer to the puzzle? Thanks.