Yes, water and dust will enter the loadbin via the openings in the tailgate. The pvc or canvas part of the ton- neau is waterproof. If you have a clip on cover fitted and you open the tailgate and look in under the cover, water will come through all the gaps where the light enters. If you have a tie on tonneau cover, water will drip through the stitching holes of the support belts stitched across the cover to hold the braces. Again if you look underneath through the open tailgate water will enter wherever the light comes in. Pack your luggage in refuse bags or plastic containers to keep water and rain off.