I recently discovered a new definition for the term "relative humidity"... I asked my brother-in-law to loan me ten bucks and he just laughed and told me, "Pizz on 'ya!"
Seriously though... high humidity will cause your coach to mildew. It is simply a bloom of all the spores which will infiltrate your coach and come to life when the right temperature and humidity are present.
Jim and Fran in Central Florida
1989 Country Coach Sedona Mark V
Turbocharged Detroit Diesel 8.2L "Fuel Pincher"