You can make patio table covers from stretchy spandex, or any other synthetic material that keeps moisture away from the tabletop. High-quality seams will resist tears and prevent water infiltration. You can prevent condensation from building up underneath your cover by lifting it slightly with a piece plastic. This will allow for enough airflow to let water and other debris flow away. You could also consider a mesh cover that allows for airflow. The cover will not blow away if it is secured with buckles or ties.