In my experience, the sheer belt-slapping, spar-snapping peaks of turbulence have come in clear air. The flight system a vertical blur and hands flailing about trying to grab at the power and the brakes have happened with not a cloud in sight.
When this hits wing resonance, they really do start to twang.
One time we put ten miles between us and the core of the CB which was way below us. We could see it on radar and flashing in stratus below. Suddenly we descended in violent lumps just like crashing down concrete stairs 1,000 feet a step. My jacket swung on its hook and almost hit the roof. No record of negative g on our old BAC1-11, but it was more than a little.
I fear that often the damage done to aircraft is caused by attempts to correct unusual attitudes. I'll risk stating the obvious, but it's vital not to be blinded by the flashes, and also vital not to try to correct a severe upset too quickly.
I'll stop now before I'm tempted to say what I think about the removal of good old tied-gyro turn indicators.