Acceptable humidity level inside TT for winter storage?

Typical residential humidity levels are anywhere from 20%-45%, depending on climate and season. Up here, in MN, many houses have humidifiers to raise the level of humidity inside. The ambient cold temps and low RH are <15% in the Winter.

Most of the materials inside an RV are the same or similar to residential materials. I would think a target of 40% or lower will be adequate to not harm anything inside the RV. A dehumidifier would probably be necessary in the PNW.