I live in the Puget Sound region of Washington State, in the Pacific Northwest - meaning it rains A LOT here! Mold and mildew are an issue as expected too, especially for an outdoor product. This Sunbrella product works great. It sheds the water like you wouldn't believe until you saw it. I also breaths very well, as I have not had any mold or mildew issues to date either. I also have a full boat cover made of Sunbrella, which works just as well and is the reason I bought the outboard cover in the same material. I highly recommend it.