Insulation in Western WA - Do I really need it?

I've got an old 1930s/40s homemade masonite teardrop without a stitch of insulation. I'll be camping all over Washington - some hot Chelan days, some mild coastal ones. Will insulation do me much good, or can we get away without it here in the Great Northwest? I'll have an old Hehr roof vent, and have a large door, two hopper-style windows and a screen pass-through between the cabin and galley for ventilation.
Someone could retrofit AC or a fantastic fan someday, but I probably won't do much more than rewire the simple 110v system now in place.
I may sell it, would no insulation be a dealbreaker in Western WA, even if it's a restored, historic trailer? I'd love your input. And oh, here are some pics:

Someone could retrofit AC or a fantastic fan someday, but I probably won't do much more than rewire the simple 110v system now in place.
I may sell it, would no insulation be a dealbreaker in Western WA, even if it's a restored, historic trailer? I'd love your input. And oh, here are some pics:

