Purchase vinyl tablecloths from your local dollar general store for your lawn furniture covers. Be sure to pre-measure your furniture to allow the covers to reach down to the ground on all sides once the furniture is covered so you know what size tablecloths to buy. This will keep rain, snow and the sun from creeping underneath and getting on the furniture. Choose tablecloths that have a soft backing on them. Usually these tablecloths are a little thicker than plain vinyl ones and the soft underside will keep your furniture from getting scratched. This will work well especially for painted furniture.
Transfer the measurements from your furniture to the tablecloths and cut your fabric to allow for draping on all sides. Leave 1/2 inch extra on the edges you will be sewing.
With the soft side of the fabric facing out, sew all cut pieces together that are needed to make a large enough cover for the furniture. One side can be left open and made to close with Velcro to allow the covers to slide down over the furniture more easily.