Hi Suzy,
You didn't mention how much snow you have on the ground - usually that helps sooth the 18 degrees below zero, but not much.
Here in Fairfax we have, at least at my house, probably a couple of inches of snow on the ground and below are the conditions:
(http://www.vtgrandpa.com/newsclips/wea080124.jpg)
Last night when I got up in the middle of the night, it was one of those winter nights like we have up here in Vermont and been having lately where you can see everything quite clearly - Almost like daylight.