coming back from snow shoe, I think it was about 30 degrees... I drove with no top, no sides, no windshield
Used bike helmet, 4 layers of cloths, ski gloves and neck cover. Never felt cold at all.
But, this winter, I'm one of the "jack stand" guys. If the car has to be down at any time, i'd rather it be over the winter, because come spring, I better be driving.