This is a known vanilla issue that happens without the mod.  If you have wetness turned on without SSAO, you will get the all white screen whenever it rains. So if you want to turn on wetness, you also need to turn on SSAO.  Rain Occlusion must also be ON.

Oddly enough, others have said turning wetness OFF fixes the issue.  It's all over the Internet right now, Bethesda needs to patch it.  Try combinations of these settings and you should be fine.

You can see articles about this dating back to the launch of the game, for example: this link / fix on the Steam forums.