An extendable cover system and method for extending a cover over an opening is provided. The system includes a plurality of panels oriented horizontally and stacked vertically at a side of the opening, with each panel held by a corresponding panel holding arm. One or more guide rails extend across the opening to receive the panels. A panel moving mechanism moves the panels one-by-one onto the one or more guide rails. Each time a panel is deployed, the panel holding arms are lifted vertically to align a next panel with the guide rails, the next panel is then deployed, and the process continues until the opening is covered.