Parking Surface can effect an RV

My real life experience is parking in Western Washington State the entire thing will be damp for months at a time. The rare occasions it is not it is either a) August, or b) below freezing.

I don't worry about it, have never worried about it, and have never experienced an issue. If you park on grass here you are more likely to have problems with a) your grass ruined with an RV sunk in it, or b) Your RV stuck sunk in grass.