An in-use cover for an electrical junction box, where the cover cap is selectively attachable to and removable from the base plate through sliding engagement of channels on the perimeter of the base plate and ledges on the perimeter of the cover cap. The cover cap defines a hollow interior that overlays one or more component ports in the base plate when attached to the base plate. The cover cap has a bottom cut-out configured to accommodate plugs or other electrical components connected to the electrical junction box. The base plate has a bottom ledge configured to engage the bottom cut-out. When the cover cap is fully engaged in the base plate, the hollow interior and any electrical components contained therein are effectively sealed from intrusion of most moisture.