Are JanSport packs waterproof?
I have good news, and bad news! All of the fabric JanSport uses are coated with about an ounce and a quarter of polyurethane, which produces a minimum waterproof rating of 40 mulleins. (The U.S. Army considers 25 mulleins waterproof!) Now for the bad news. Even though the fabrics are perfectly waterproof, sewn pack products never are! Wherever there are zippers or stitching, water finds a way through. The only true waterproof packs are made of vinyl and have sonically welded seams, like a dry bag for kayaking. Most serious backpackers recognize this limitation of sewn packs and carry a rain cover made of lightweight nylon that can be seam-sealed easily. Some of the people I respect most simply carry a large plastic garbage bag, slit up the back, and some duct tape. Using waterproof stuff sacks to organize your load is another solution.
