Close your umbrella and measure it from the top of the umbrella down to the end of the fabric. Double the measurement and add 6 inches.
Choose a waterproof fabric. Waterproof outdoor fabrics are available at fabric stores, or you can use a plastic tablecloth or a shower curtain.
Cut a circle from your fabric that is the diameter of the measurements you took from your umbrella. Mark the center on the inside of the circle with a pen or marker.
Cut a strip of fabric that is long enough to wrap around your closed umbrella with an overlap of 4 inches and is 2 inches wide.
Sew one end of the fabric strip halfway between the center dot and the hem of the fabric circle. Sew a 2-inch length of the hook side of the tape to the other end and sew the corresponding loop side over the the other side of the strip that is sewn onto the fabric circle.
Place the cover over the closed umbrella with the center dot over the top point of the umbrella. Wrap the closure strip around the umbrella, gathering the excess material of the cover as you do so. Secure with the hook and loop tape.