Buy an inflatable so that you can store it away from the sun...
Seriously, if the board has been exposed to UVs to the point of destroying the paint, the damage probably isn't limited to just the paint...
You can try to remove all the paint, (sanding? solvent F? Turps? ... anything but not acetone), then re-paint, plus UV-proof varnishes... But is it worth it?
Try to use at least a reflective survival blanket/bag, with something to keep some airflow between it and the board.
PS: read
www.standupzone.com/forum/index.php/topic,37449