Here' what I did for my grill that was left out in the wind, rain, and snow when I lived in NH. I went to Home Depot, got one of the heavy duty tarps to fit (not the blue ones, the brown or silver heavyweights), got bungy rope off the reel sufficient to go around the unit, and two bungy hooks. Hard-core hardware stores are probably a better source.
Lay out the tarp flat on the ground. Starting at one end, thread bungy up thru an eyelet, pull to the next and thread down, etc., alternating stringing the bungy rope all the way around the outside of the tarp until you come back around to the original end. Lay the tarp on the grill or 'que. Pull the bungy tight and install the hooks so they hook to each other. Release to remove the tarp from the thang being covered.
Not only does this method hold on the object in a good wind, but it lasts for a long time, and doesn't have the felt line in it that gathers moisture and freezes to the steel -- rusting and ripping in the cold.
That's my story and I'm sticking to it.