That helps cut the drying winter winds a bit. I haven't seen a humidifier but as soon as the water is on in the spring, these guys will soak the hulls, mostly filling the bilges, to slow down drying.

Some wooden boat storage has gravel floors that keeps the moisture levels higher than concrete. It's the boats like the one I posted that dry out the most. They're inside a heated space during the winter getting worked on. This is the second one I've seen "dipped" to get the wood swelling. It can take a while if the planking is very dry.