Most new cushions are covered with coated or treated strong synthetic fabrics that are not damaged by summer weather and can be left outside all season. Polyacrylics that feel like cotton but are water repellent and mildew resistant, and open-weave polyesters (like tire cord fiber) coated with polyvinyl chloride (PVC), or vinyl are easy care.
Fillings are polyester which resists mildew and doesn't hold water. Seams should be stitched with polyester thread, and have buttons that allow water to drain out bottom.
Care Cover cushions with towel if you have on suntan lotion. The fabric, and sun lotion, when hit by sun's ultra-violet rays create a chemical reaction that stains the fabric.
If wet by a heavy rain, dry cushions faster by taking out of frames and standing up on sides.
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.
Some manufacturers recommend "deep cleaning" cushions at the end of the summer with a solution of 1 cup liquid chlorine bleach and 1 cup powdered laundry detergent to 3 gallons warm water. 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. Then rinse thoroughly with cold water. Dry several days in sun until thoroughly dry all the way through before storing. Follow this process ONLY IF recommended by manufacturer of your new synthetic cushions. And NEVER put undiluted chlorine bleach on cushions; dilute in water as directed.