I had a garage studio in North Idaho for two years. I had a electronic kiln with a vent system to outside. I had to make sure the vent was high enough so snow or ice did not get into it. It fired fine during the winter months, but I did run a slow cooling program for the temperature range I was firing. The main thing was protecting it from moisture and it was on a cement floor and I made sure it was away from anything flammable. I also hired an electrician to do the electrical work for the hook up of the kiln in the garage. I would also fill the kiln pretty tightly during winter with work so that would also slow down cooling time. Good luck on this process.
I just joined to try to help. I just started working here in eastern Tennessee this fall. I have used big ceramic store for years when I was out west. I did see you mention clay king and they have been extremely fast on orders. There is also Highwater clay online and nearby. Also, if you are near Knoxville there is Mighty Mud if you visit them rather than order online. I have been getting my clay from them. Farther, but if I am driving there anyway I plan to stop by Kentucky Mudworks in Lexington soon and they have an online site I just have not used them yet. I am also working on testing clay here in Cumberland gap since there are local deposits.