Short Answer: Outside roasting is not advised. This might be a compound problem, and one we have seen with other coffee roasters too, especially air roasters. The first issue is ambient temperature. Higher velocity roasters like Popper will definitely roast differently when surrounded by colder air. The second issue is often the quality of the electric supply in a garage or patio etc. Popper, and other roasters, need a good quality 120v outlet, and garage plugs or outdoor plugs are sometimes not the best. There's a safety concern too : Our experience is that people sometimes "take a break" from watching their roaster when they somewhere cold. We had a guy doing winter-time roasting on a patio table, but would sit inside where it was warm. Even though he was "10 feet away" he really couldn't hear, see or smell the roast, and the coffee charred to a crisp and partially melted the machine. DON'T be that guy! If you roast in a colder environment, you need to be doubly careful to watch the machine. They roast is absolutely going to be different. And the thermal sensor on the machine likely won't regulate the high temperature in the same way when it's cold out. I am sure there's a safe way to manage all this, but please be aware of the risks in roasting in a garage or other colder place, and stay with your roaster at all times!