I keep them in the house, you can keep them in the garage if it is warm enough. I would keep them in a Tote/storage bin from walmart, and is not see through. I would use a Ceramic Heat Emitter on the top of the lid (Cut a hole in the lid and put some screen down for the lamp to sit on). Fill the tote with cardboard and some food and water. You can do a number of things to heat the bin, undertank heaters, heat cable, basking light, red heat lamp, Ceramic Heat Emitter, etc.
Hope this helped.