During the winter months, there's nothing to stop you from packing away your wooden garden furniture and storing it in the garage. Otherwise, be sure to cover garden furniture. This will protect it from rain, which can cause wood to shrink, warp and bend. If you are planning to leave it outside during winter for long periods of time, covering it with a sheet of tarpaulin or otherwise is recommended, but not needed. It'll help to protect it from bird poo, leaves, moss and other stuff though, so if you can get a cover, we'd say do!