Windchill is absolutely irrelevant to a car starting. The actual outside air temperture counts not the wind derived # freezing human flesh. A prius is a fine choice. Basically it sound like you get below 0 weather eg -20F occasionally with lots of wind.
I would suggest using synthetic oil for the winter as engine cranking is much easier on vehicle and your battery. Also a good set of winter tires over all-season tire rubber not just for better traction in snow/ice/slush but that the tires rubber can handle cold better. Basically winter tire’s rubber is optimized for cold temps while all-season rubber turns very hard at cold temps and loses traction easier on wet/dry pavement.