The weather effects are currently planned to be implemented in specific zones with the 1.10 patch. We will closely monitor the effect it has on the game and continue its development accordingly. It is of course meant to be an enhancement so it is important that it remains as such. Consider it a "wet run", get it? Water? You can get a taste for the effect from the videos we put up last week and on the Under Development page: http://www.worldofwarcraft.com/info/underdev/ The effect will indeed have an option to toggle it off if necessary or desired.