I live in Boston, and have no garage. My Z3 survived the winter outside without trouble. The main problem is removing ice from the plastic rear window, because an ice scraper would gouge the plastic. One solution is to hit the window from the inside to knock off the ice. An even better solution is to turn on the heat to melt off the ice. Another possibility would be to get the removable hard top, which has a glass rear window and electric defroster. This is a ~$2K option.