Black and White did stuff like that with weather. Problem was that weather is generally pretty consistant in a lot of places in the world for the time you would actually be playing a game so you'd never see rain or anything if you played with the real world setting on. I guess it would work for something like a sports game where you play a little every couple days over the course of a year, but not for something you're addicted to for a couple weeks and then drop it. Even still, if you live in a boring place weather-wise, your game is going to be pretty boring. More often than not I'd rather have the developers come up with a weather patern because it'll give you a more interesting mix of things for the most part.
