After storing a project car outside for years in one of these tents, here's my advice. If it's a nice finished car, pony up for indoor storage. These tents are flimsy and prone to failure anytime. The wind takes a toll on them the most, you can secure the frame as much as you want, but the cover still gets loose and rubs on the frame until it tears. The good tents with the gray covers, well the covers only last a couple years at most. Snowload is another issue unless you pay even more for a domed top one.
So I'd tarp it up if it's a crappy paint project car, or pay for indoor storage if it's a nice car. The whole thing is kinda useless if this happens to you.