It isn't a popular problem but does happen to cars and SUV's, for different reasons. You may want to inspect the windows for rust and seal failure. Check the rear hatch area. Inspect the weather stripping for tears and debris (dirt, leaves, or pine needles). inspect the rear brake lights (they may not be seated correctly and could allow water to enter). You may want to try having someone sit in the affected area (with the floor dry) and either run water over the to SUV to see if they can identify the source. An automated car-wash may work better. I hope that helps. Please let me know if I can be anymore help, good luck.