I used to have a cover on mine, but the cover eventually deteriorated and I've never bothered replacing it. As a result, it's been years since it's had the cover on, and pretty much I've found it doesn't make any real difference, and we get the whole spectrum of weather here. I do sometimes get water in the drip tray when it rains, but I've never really had problems with it making a huge mess (quite frankly, the birds that perch on the deck railing make more of a mess). We did seem to have more problems with wasps making nests in the grill when the cover was on than we do with it off.