Before I did my insulated shop workroom I kept my molds, plastic, components like colors and glitter and hi lite....everything , in the house and took only wht I was going to work with out to the garage. I'm in Minnesota so I'm pretty well versed in working in the cold myself. You sort of have to find out what the plastic and you will tolerate as far as being chilly but I would keep the molds and materials inside at room temp until its show time then go like the blazes. Plastic if cold then heated quickly can develop bubbles from moisture so at least keep that warm. When you see the 40's and 50's overnight then you can leave the plastic out.