Good idea to ask the person who does my regulations. I live in southeastern Pennsylvania, where the summers are very humid. However, the indoor air in winter is quite dry. I have an evaporative humidifier set up in the room, which seems to keep the humidity level around 50%.
The person who does my regulations got back to me and said that between 40 and 60% humidity is optimal. One of my harps came from Florida, too…and I also have an acoustic bass in the room, coincidentally (my boyfriend’s)!