I will second the suggestion for a maxxair vent cover...just installed a couple myself....very easy to do and it will protect the other cover and prevent the sun from beating it up, will protect it from stormy weather, hail, etc...and best of all will allow you to leave that vent open and not worry about rain coming in. Greatly increases ventilation. Only thing is, judging by where you have it parked you may no longer have the clearance to park it there once a Maxxair is installed....loks awfully tight.
2011 GMC Sierra 2500HD
2014 Rockwood 8289WS, Diamond Pkg.