When it rains, rain falls in the house has a roof.
Edit By Crinrict: Adjusted Title, Added tag.
Ideas
Mine has also been affected by this. Things I've done to try to resolve is: repaired game, checked roofs are still there, going to manages world's and back. I even think I had a sim get struck by lightning while inside.
I had a few mods but removed them and been playing without mods for awhile now.