Even optimized dynamic weather - as cool as it will be - is just going to be a resource hog. Overall I'm very optimistic about the performance CoD is going to have on relatively new systems judging from what I've seen so far considering the incredible amount of fidelity and detail we'll see in the DM, FM and (hopefully) AI.
Just be prepared to make a few compromises in the details, effects and maybe even sub-native resolutions to keep a decent average framerate.
I'd like to see Ilya's system there with low altitude flying over cities though.
