Cover the windows to reduce the amount of cool air that enters the motorhome. Cover the inside windows with foam core board or Velcro a piece of plexiglass over the window.
Cover the windows in shrink film. Buy a roll of shrink film and double sided tape from the hardware store. Measure it against the window. Cut the film down to size and then stick it over the windows with the double sided tape.
Insulate the roof vent with the shrink film, or tape pieces of pillow cushion over the vent. Buy aerosol self-expanding foam. Seal the gas and water lines that have vents which can release cool air into the living area.
Weatherstrip the entry door. Check it for air pockets. Weatherstrip the door jambs from top to bottom. Try to cover each side with one long strip to avoid creating your own air pockets. Check the door to make sure it's not difficult to shut. If it is, remove some of the stripping.
Run the exhaust vents when cooking and bathing to reduce the humidity that can build up inside the motorhome.
Avoid heating your RV with methods that produce large amounts of water vapor, such as propane tanks or the stove top. Use electric heaters if you need to bring an additional portable unit. Watch your usage, as RV parks may charge extra for consuming a lot of electricity.
Crack open your roof vents to give the moisture buildup a way to escape. Leave the roof vents open all day. Close them at sun down and during rain.
Run your exhaust fans whenever you cook or bathe. The moisture released in the air when you engage in these activities will be sucked out immediately.
Open your windows when the air is dryer outside than it is inside. When you close them, go over the surface areas of your motorhome with a dry towel to prevent condensation from building up.
Leave the main back window and the main front window open at all times. Keep them cracked about an inch each to keep dry air circulating in to move the cool air out.
Use a dehumidifier. Set it at your desired humidistat reading, which is like a sleep setting that keeps it from running indefinitely.
