When we store ours in winter we leave all the interior doors and drawers open and have 3 of the crystal type dehumidifiers. We had no condensation whatsoever, we stored outside up at Pender Harbour Sunshine Coast so same climate as yours. We cover the mattress and furniture with plastic.
Right now we are at 6500 feet in Williams Arizona and it drops to 32 overnight, putting on a shirt out of that wardrobe in the morning is an experience
but we have not had any condensation in there.
The only time we notice condensation is when it is very cold and we cook and forget to use the extractor, then we get it on the windows.
WELCOME to the forum, we can see the mountains behind you from where we live. We camped near the Tyee club a few months back!