I'm tossing around the idea of turning a small storage building I have into a home studio. It will be pretty small but I plan on making a room on one side of it and of course insulating it pretty well. My worry is the equipment sitting out in the building. I know the speakers and mic especially would take a lot of abuse in the change of the temp and humidity.
What I'm wondering, what is "ok" temperature and humidity range for storing equipment? I live in the Mountains of North Carolina so we have a range of hot to dry days and our summers can get up to the 90s while the winters can drop to single digits for a few days in a row. I would have heat to make it comfortable to work in but when I'm not using it, I'm wondering if I have to keep it "controlled"

Thanks