We had some fog with the recent snow. Was that a freezing fog outside, or a frost fog? Here in Kansas it is VERY unlikely that we would see a frost fog. A freezing fog occurs when the suspended water droplets, or fog, freeze on contact. Usually temperatures are at or slightly below freezing. Frost fog, however, occurs at very low temperatures, and usually in clear calm weather in the high latitudes. It is rare at temperatures warmer than -20 °F, and increases in frequency with decreasing temperatures. At -50 °F, it is almost always present when there is a water source, such as open sea, herds of animals, or volcanoes.
Mary Knapp, Weather Data Library