A sectional storm panel for covering an opening in a building is formed of a plurality of vertically elongated, narrow, corrugated panel sections that are manually assembled, in edge to edge relationship, from the interior of the building, from each side edge of the opening towards the opposite side edge to form a pair of co-planar panel portions that are spaced apart. The space between the panels is covered by a separate cover section that is inserted through the space, from the interior of the building to the outside of the building, and then positioned manually so that its vertical edges overlap the adjacent panel section vertical edges that define the space between the panel sections. The sections extend between a lower rail and an upper rail secured to the lower and upper edges of the opening, respectively. Removable mechanical fasteners are manually applied, from the interior of the building, to fasten the sections to the lower rail as they are assembled to form the panel portions and to secure the cover section in its place.