I realize that a lot of folks have no choice .... but I would never store our RV out in the sun for weeks/months/years at a time. Nor would I buy a used one that I had any idea had been stored this way. The sun's UV rays are a killer and they do irreversible damage .... plus, how about the tremendous heat buildup in the interior in a sealed up RV stored out in the summer sun?
We store ours outside, but with about 75% of it under the shade of a large oak tree and with it parked so that it's areas most vulnerable to UV damage (the cabover window and it's seals, as well as the whole cabover section) are always shaded by the tree. We would not have spend our hard earned dollars for an RV if we would have had to leave it stored out in the sun 24/7. RV leaks are our worst nightmare and UV rays are terrible on sealants over the long run.
