Abstract: A storm window having a peripheral frame including an integral, angulated leg portion for extension, abutment and securement to the jamb of an interior window. The storm window of the present invention includes a window frame extrusion having a plurality of integrally formed slide tracts for receiving a window unit therein, and an inwardly facing flange portion extending therearound at a selected angle relative thereto. The angulated flange includes an outer planar flange portion in generally parallel spaced relationship with said slide track portions for direct securement to a window jamb of an existing window. This particular construction facilitates the flush securement and sealing of the storm window of the present invention to the existing window in a manner facilitating installation and reducing thermal conductivity between the adjacent window structures as well as air infiltration therebetween.