The storage areas on a boat are reserved for those spacial odds and ends. They make use of otherwise hard-to-utilize places, usually up against the hull.
We heat the boat to a very comfortable temperature, and keep it that way. But the "stuffing" in those compartments acts as a very effective insulator. On the outside wall of the compartment, the hull is at essentially the outside air temperature, which could be below freezing. At the inside of the door, the temperature is pretty close to that in the living space. So, the temperature falls thru the clothing, from the inside temperature to the outside temperature.
Next fact: We try to minimize air exchange with the outside - after all, the incoming air is at outside temperature. So, the moisture produced by two healthy bodies breathing, and that which escapes from cooking ("simmer for an hour until the sauce thickens" just means to boil off a lot of water from the sauce) all remains inside. Finally, when we burn propane inside (the stove burners, but much more importantly, the oven), all of the moisture from that ends up inside too. So, it is not unusual for the windows to fog up during cooking, or when someone is showering. But after a while, they clear.
So where does that moisture go? It migrates to the coldest places on the boat, where it condenses back to liquid. Yes, you got it: those storage compartments against the hull. At some point, the temperature profile thru the clothing will drop below the dewpoint. Everything you want to keep dry in those compartments had better be enclosed in plastic - plastic ziplock bags (they come in all sizes - some really huge!) and tupperware containers (there are some really nice ones) are your friends.
Now, I don't want you to get the idea that we live in a sauna - not at all. But you won't find boats with humidifiers onboard either.
In the galley, storage deals with a slightly different problem: weevils. These tiny creatures seem to appear spontaneously in almost any food item, but most commonly in the grain-based: rice, cake mixes, flour, crackers etc. The cure for them is easy, and almost magic: bay leaves. If you put a bay leaf in any opened food item, it will stay weevil-free. No, I don't know why it works - but it does. Jane even has bay leaves scattered on the pantry shelving, for good measure.
Two simple things, bay leaves and ziplocks, make all the difference in boat life in the winter.