The switch will trip the GFI if connected. Outdoor should already have a GFI on the un-switched circuit. You can't run 2gfi on the same circuit, so be sure there isn't another outlet on that circuit. They can get pretty weird, particularly on 50's-70's construction.

My deck outlet is run through the GFI in the master bath, the half bath is run through the basement/ sump gfi and the kitchen isn't protected so we're having to get a gfi panel breaker during the upcoming remodel.