Thanks! When it is this cold my wife and I stay at home and sometimes my wife wears heavy winter clothing and walks to one of our neighbors who lives across the street. Our neighbor loves Alaska, but she dislikes the cold winter temperatures. She won't even walk to our house, and sometimes drives her car from her house to ours
Most times I have noticed that the ice fog in the interior of Alaska where I live, happens at the ambient temperatures near the minus 30's degrees and colder. It is certainly present by the time the temperature reaches -40º F (-40º C). As far as I understand it, this fog is comprised of crystalized water vapor. In this case any moisture is the air turns to ice, including the moisture from automobile exhausts, from boilers and furnaces, power plants, even one's breath, and so on. Somewhere close to -40 degrees and colder, one can toss hot water or coffee in the air, and it almost instantly turns to ice fog. There are some videos about this subject floating around in YouTube