My dad used to sleep in his car at Blackwater Falls on XC ski trips when it would be like -10...I gather the need to urinate was the only thing that finally got him out of the cozy cocoon of the polar sleeping bag in the morning. Amazingly, the park has year-around hot water showers in the bathrooms at the campground, so one's chances of survival went up considerably after the freezing first piss of the day.
6 degrees at Timberline this AM. 7 inches fresh, awesome conditions.