(Device: iPhone 6S+)

When first entering the world while it is raining, and while under cover such as a cave or house, there will be rain inside (with sound) until you move off the block you are on. the first 2 photos show the rain and that you can look around without stopping the bug. The last photo is when I moved 1 block forward which caused the game to update and fix the rain. This also seems to happen when crossing a chunk border and still under a roof.