I camped at Horns Pond (Maine) last February during the cold snap. For some reason, the info board there had a thermometer attached. It bottomed out at 35 below around 9:00 pm. Our own thermometers all did the same. I don't really trust any of them, but suffice to say, it was cold. However, it was not particularly uncomfortable; I've felt colder and more miserable at 5 below, or even 10 above.
Assuming you have the right gear, facing cold is mostly about attitude. And, I find that the best way to sleep warm is to go on a short, starlit snowshoe walk, with all your layers on, before getting into your sleeping bag. Just don't overheat and sweat.