I think it's a great idea and wouldn't need to be overly complicated. Someone mentioned 'extra resources to get live weather information'. What resources? Wind speed is 2 figures. A weather chart can be captured in a 256x256 texture and read by the engine. That's all the data that needs to be passed from weather site to server to client regarding the weather conditions.
Of course, getting weather conditions at all (non dynamic) implimented very well should be the first concern, and this a neat after thought.
I've always thought the realtime day/night cycles should be implimentable, though.