I have stored my boards wet in bags in my van and leave them there constantly, and I have no garage so my van stays outside in the sun.
Never had any issue for 10 years, but I always leave the bags open on at least 2'. Also my boards are stored sideways (on the rail) with fins on, with the open portion of the zip on the top (basically from the bag side handle to the tail), to help hot air circulate out of the bag, and the bag cling less to the deck & hull of the board. Also my van is windowless. And on dry windy sunny days I open all the doors to let it dry.