Well, adding more detail into the game is always a good idea.
But maybe, just maybe not to Fluorite or Bonfire. xD
Weather adds lag, maybe not much. But if most of the maps had this, it would still affect the whole game/server.
And honestly, Fluorite and Bonfire are bad enough, right? Right..
But I'd be fine with it if weather would be added to.. let's say, Temple, Cape, etc. c:
Nice idea. ^^