Abstract: An adjustable auxiliary window element is provided for easy installation in and removal from a window frame, and particularly for use as a storm window device. The auxiliary window element includes a window pane which is perimetrically encased in side, top and bottom channel members, and four corner members, and a pair of cover channel members, each adjustable disposed so as to cover two corner members and a side channel and adapted to snugly fit in a window frame. The corner members have resilient members secured thereto which bias said cover channel members outwardly.