My daughter & I built a wood rack for my kayak & canoe this past spring. There is a wood fence on one side & trees near each end for some shade.  We have the rack covered with a tarp that does not contact the boats. However, with rain I will need to put more cross bars at the top of the rack so the tarp does not collect too much rain water.

Ralph

   I wouuld suggest a cover over the cockpit to keep varmits from nesting there.

What Grumpy said, but be sure it's breathable fabric. I'd also occasionally check it to clean out the cobwebs and any really persistent or smaller critters that made it past the cover.

Laszlo

   Now we store our kayaks under our deck upside down but at our last house I made a fence cradle for each kayak out of two vertical 2x4's per kayak hinged at the bottom with a strap going from the top end of the 2x4 to the fence..also like above, had a tarp from top of fence draped over kayaks with a pvc pipe between the 2x4's to keep the tarp off the kayaks.

I know you said the garage needed to be vacated for the next project but maybe it is just a floor space problem.  I use this system and hang three in the garage. Of course there are four so one is on the floor now. I also have a hoist system but it hasn't been moved yet.

   http://talic.com/product/kayak-condo/

   I agree with Grumpy, keep your boat inside.  I use a great rack system made for closet shelves.  Home Depot or Lowes, the closet tec hanger bar screwed into each stud is super strong, then hang the shelve tracks down wherever you want with one inch height increments, get as many 24 inch long shelf brackets as you need, stick em in and put a piece of pipe insulation as padding, throw your boat on it.  I have an 18 Chesapeake, a 17 Chesapeake, two 14 foot Kaholos, a DN Iceboat w mast and plank, and seven surfboards all on the rack.  Safe and sound, solid as a rock.  After screwing around with racks outside, tarps, bugs, animals, water, leaves, mold, dirt, it just isn't worth keeping a small boat outside.