You might not think it necessary, given that the cover’s primary purpose is to be constantly exposed to rainwater, but you will find that your cover picks up dirt and may even become musty and risk mould if packed away and used continuously. As a first port of call, check the care instructions provided by the manufacturer as these will be specific to the material your cover is made from. Otherwise, wash by hand in the water, without detergent or bleach. Research the particular type of fabric used to find best care instructions. Some users do put theirs in a washing machine (we’ve heard of them being bundled in a sock!) but we can’t endorse that across the board. If you do machine wash, avoid using detergent or fabric softener as they can damage the coating and treatments which make the fabric waterproof