hardware rendered streak particles will do the rain for you. You could have multiple rani layers (front medium and far) do some post work on them to blur them and colour correct them a little.
As for the puddles that's a bit harder. but an animated texture on a simple plain would probably do it. depends on how much you want to get into it really. I remember seeing some tutorials around someplace a while ago. Do a search on google for them I guess.
Hope that helps
Alan
Technical Director - Framestore
Currently working on: Your Highness
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