Weather in my corner of Oklahoma is 28 degrees rn and I'm currently drying in a broom closet right now so I have no insulation. I might add that I live in a house that isn't completely insulated (hunting cabin converted into house) so I'm wondering if the colder temps would hinder my cure. I'm still keeping 50%Rh but the temps concern me just a little bit
I think the really cold temps don't necessarily hurt, they make it take longer to dry for sure, but I have never had mold type issues pop up due to cold weather. *watch for extreme fluctuations though.
I dry out in my garage and during the winter it's probably around 40 or 50, RH is low here. I just wait till the buds feel dry on the outside (if you can stick them outside for a few hours on warm sunny days that helps), do a quick final trim and then into jars/paper bags; going between the bags and jars until it gets to where it should be and then into jars. It's more shuffling back and forth than I would like, but I would rather take it early.