The low temperature at the Fargo COOP site has been below zero on 28 of the past 30 days. So no, it has not been your imagination that the cold has been persistent for a long time. Plus, another cold front passed through the area yesterday, meaning today is the 29 of the past 31 days with a minimum below zero. In total, including today, Fargo has been below zero at some point on 36 days this winter. The long average is 47 days, so we still have a ways to go to get to that point, but considering how cold we will be in the upcoming days, getting to that average seems fairly likely. Back in winter of 2013-14 Fargo was below zero 57 days to this point in winter.