My S9's are located inside of my garage. They are from the March batch. The garage is a single car, open attic. The temperature outside was around 20 degrees fahrenheit when I first turned them on. All I did was place a space heater in the garage for about 4 hours (I was inside of the garage) and let it warm up. I highly doubt my air temp was above 45 degrees, and my machines fired right up. They started to hash right away.