WeatherTalk: Arctic air is more than just cold air
Arctic air is air which has come to us directly from that area around and north of 66.5 degrees North latitude.
To most people, the term, "Arctic air" is a vague reference to very cold wintertime air from up north. When the forecast calls for Arctic air, the general expectation is for weather that is consistently near or below zero degrees Fahrenheit. By definition, however, Arctic air is air which has come to us directly from the Arctic, that area around and north of 66.5 degrees north latitude, or about 1200-1400 miles north of the Dakotas and Minnesota.
At this latitude, there is barely any daylight for most of the winter. In the dark, with everything covered in snow and ice, it gets very cold, particularly underneath a clear sky. Our coldest winter air outbreaks happen when Arctic air that is particularly cold is delivered very quickly, leaving very little time for it to be modified by sunshine or mixed with other air on its way here.