I just leave my open bags sitting on my patio opened, but then again its really dry here in AZ. Even if it gets rained on, it is dry within half a day. If I lived in a more humid climate (I used to live in MD) I would definitely keep the bag as closed as possible except for when I am pouring coals out of it. My unopened bags are stacked nicely under my desk in my office/spare bedroom. If I was keeping opened bags in my garage in a humid climate I would get a Tupperware bin or a bucket with a lid to keep it in.