I JUST moved my 8 footer out of the garage this weekend. It was epic hell and almost 20+ hours of work.
If the garage can be well ventilated and insulated, then its cool. But mine has a metal door so whatever temp outside was in the winter, it was also in on the inside. And whatever temp outside for the summer was, it was even HOTTER in the inside, like +10 degrees.
During the winter, if you dont have a room heater, condensation will build heavily, rust metals, grow mold, and soak the walls and doors.
thats if your garage has a metal door and very little insulation