I was flying on a 90nm cross country on Saturday, on a beautiful day. There was a high level Airmet for turbulence but nothing for low level. I noticed that as we flew toward our destination some fair weather cumulus clouds, not convective looking at all. I did notice that as we neared I was at about the same level as the clouds, so I started to descend a bit to stay clear of the clouds, as I looked out my left window, I could see a cloud in the distance and we were level with it, so I I began my descent and suddenly we hit some nasty turbulence. The right wing dipped to about a 45 degree angle, and it startled us at first, then I corrected it, then the turbulence continued. I descended hoping out of what I thought was wind shear, because of the cloud level. I descended 1000 feet and there was still pretty rough turbulence. I finally aborted and turned around and as soon as we cleared the front edge of these few clouds, the turbulence was gone. We had a few thermal bumps but nothing like we had just experienced. I am concerned as to why this occurred with these fair weather cumulus clouds moving in and it was something I had not encountered before. Can anyone tell me, is this a freak thing or is this normal ? I have tried to google it and I know if you fly under the base of cumulus cloud you could have a rough ride, but this was in the clear with very few clouds moving in. Winds were 16knots at our flight level, no big deal. Can anyone explain what might have happened. I am a new pilot, under 100 hours, and I handled it well, but scared the crap out of me, because it was tossing us around quite a bit.