The coldest I've ever skied was at Stowe (wintr 96-97), -20 something air temps, and -84F after windchill, they had one lift open because of wind, and after taking a first run, got on the chair for a second, got to the top, no one was there, skied down and went in and found out my roomate and I were the only ones who took a second run that day, they closed down at noon because no one would ski and keeping the lift open was questionable at best with the winds.
However, VT doesn't get that bad typically. Some areas are typically colder than others, but having moved out to CO and seeing some -20F temps at night recently, its not as bad as VT. I think it has to do with the humidity and the cold, low humidity and cold temps, not that bad, cold temps with higher humidity can cut through you a lot quicker.
Most important though is just simple proper layering.