Help PLEASE, With A Wet MAK!

I really don't know what to do! I've covered my MAK with everything I can think of, including the OEM cover, plastic and a fiber-backed vinyl cover, but nothing is keeping it dry underneath. When I remove the cover, water is dripping on the outside of the grill. Inside, the grill grate is moldy. A few leftover pellets in the hopper appear to be slightly swollen. It can't be good for the electronics either.
I store my bags of pellets, charcoal and a Primo under a heavy duty tarp. When I lifted the tarp to check... moisture everywhere! The bags of charcoal feel damp. I know I'm destroying my 10 or so, 40# bags of pellets. Thing is, last winter, I didn't seem to have this problem under the tarp. Now, all of a sudden, this winter, everything is wet! If I had room in the garage, everything would be in there.
How in the world are you guys keeping your stuff dry??? It's driving me nuts! Is it a climate thing? Something different in the air from last year???

Is there some kind of small, break down, tarp shed that I can get? SWMBO will not allow me to build a proper shed, but she might let me put one up, if can easily break it down once the rainy season is over.