Lol,every time I start to curse my 6x20 tool/work shop I realise Im not working out in the mud and rain of my youth..
You could set up one of those cheap car shters to keep the elements out. Simply lay some plywood up to lay on and build the shelter.
Heck even a weather proof tarp will do. A few 2x4's,some rope and a good size water proof tarp,a bit of ingenuity and you have a home built car shelter that will likely outlast a packaged one.