I've also noticed this (at first I was like, WTF? Is it raining in my game?). If what was said above is true, that makes me sad that nothing can be done about it.
Samsung Galaxy S4 Active
Samsung Galaxy Note 2, Samsung Galaxy S II, HTC Desire Z, Nexus One (at&t version), Sony Ericsson c905a, Sony Ericsson w760a, Cingular 8125