Diversions to Wx
There's hardly a day goes by here that we don't need 5 to 25 miles off track to avoid buildups. For the most part, ATC is aware of this and prepared for it.
The way traffic flows work out here, it usually isn't too much of a problem either. But, for all of that, most of us are polite enough to either request clearance in advance of the necessity, or to "require" it if something unexpected happens to jump out from behind the bushes, so to speak.