If you have cushions filled with urethane foam, these are not completely weather proof. Neither are covers or cotton or fabrics other than those listed above. So protect such cushions from rain. Cleaning Wash with mild detergent suds and rinse. Follow label directions for other procedures.
Some manufacturers recommend a flushing with a hose to remove soil.
Be sure cushions are completely dry before storing for winter. Never wrap in plastic for storage. Store in dry place. Flush cushions with solution on paved driveway or patio, and let soak 30 minutes so bleach can destroy any mildew inside. Scrub any stains with a plastic scrub brush on coated polyesters, a synthetic sponge on the acrylics.