OOOOOOhhhhhh... Thunderstorm stories...
Like KathyLauren, I have had only 1 such encounter. On my "long cross-country" trying to get the instrument rating, we were supposed to go RAL --> SMX --> (Rialto) --> RAL. Before we left, we did all the standard pre-flight work, and of course there were no reports or forecasts for convective activity within 1000 miles. Just lots of puffy white whip cream to blast in and out of. The first leg was exactly that, and was some of the most beautiful times ever. Huge cloud grand canyons. At SMX we did the drop and load (drop the coffee from RAL and load more coffee from SMX), and got back in the plane to head to Rialto. Once in the LA basin, it was solid IFR, at one point near ONT, in the space of about 5 seconds, we went from light turbulence to severe turbulence, and hail all over the plane. It was so loud that we could not hear any radio, and could only hear each other by screaming into the other's ear. As the hail lessened, in the space of about 30 seconds, the C172 was instantly covered in ice, and we were descending in spite of the full power. About 1000 feet later, and a few minutes, we popped out into the clear. And not 15 seconds after that, we hear on the radio, "Attention all aircraft, Sigmet Sierra is now in place for convective activity..." My instructor said to me, "No sh*t" which was the only time in several years of flying with him that I heard him use such language. His next words to me were, "OK. Now you been in a thunderstorm. After such good learning, don't do that again..." I have followed his guidance on that for 25 years... (Yes, we did have a longer conversation on the ground that we probably should have re-checked the weather in SMX. That said, likely it would not have shown problems...)
Katie