That said, let's move on to reality.
Thermals can offer a toss and twist as well.
Even an ostensibly calm day on the ground can have enough thermal activity to give serious challenge to the best canopy pilot among us. For example, a freshly mowed landing field on a hot summer day might give some bump and thump to the ride, and the thermal turbulence coming off the runway is different from the turbulence from the trees of the forest. Usually we can tell when it's so turbulent and that we should stay on the ground. Canopies might buckle, or fold laterally and snap back into shape with a whack loud enough to bring the morbidly curious out of the hangar, or suddenly catch a down draft causing vertical plunges of a few feet before resuming their troubled flight. It can get to be quite a circus on the landing field as jumpers still on the ground collect in ever increasing numbers by the fence to watch as, load by load, the plane is carrying fewer and fewer jumpers.