We went over a hurricane once (just the edge of it) and noticed very little turbulence. We've been in other storms where we could actually see the lightning in the clouds nearby, but I think they only do that when it's unavoidable. They can misjudge sometimes, which can result in a diversion. Once, going into Chicago, we were supposed to beat a thunderstorm but did not; the weather was too bad to land, so we circled for a while to see if it would clear. When we ran low on fuel, we diverted to Rockford to refuel and had to sit there until the weather in Chicago cleared. That's a worst care scenario...at worse, it's usually just extra turbulence.
Barb