Most FPS games I know of don't have weather as a configuration option, I've seen dynamic weather in some cases. Of course even if there's no way to have a map turn on and of particle effect based on a configuration file I don't think having multiple versions of some maps would be to much unless they took up a lot of memory. For instance, maybe having Clearcut and a version thats raining. I think one of MWDA's weather conditions was even "Tornado" though it seemed like it was intended to be the aftermath of a tornado which would be an interesting place to have a fight.