Abstract: A winterizing seal for a pool skimmer includes a cover plate dimensioned to overlap the margins of the skimmer opening and having a support portion on its rear surface which extends into the skimmer passageway. A resiliently deformable gasket is provided on the support portion and is configured and dimensioned to bear on the side walls of the skimmer passageway to provide a leak-proof seal between the cover plate and the skimmer passageway. The gasket is pressed against the side walls of the skimmer passageway by a compression plate which is coupled to the cover plate by a nut.