In the entire period of record of Fargo Moorhead, 1881 to present, the temperature has reached 50 degrees or higher just 16 times in the month of January. This is so rare that there is no measurable frequency trend except that it often occurs in bunches. It happened four times in 1900, once in 1908, once in 1931, three times in 1942, twice in 1943, once in 1981, once in 2002 and three times in 2012. The warmest was January 5, 2012, at 55 degrees.
Days with temperatures in the 50s in January in our climate all have one thing in common: an absence of snow cover. Snow cover reflects sunlight back into space, keeping the lower atmosphere cool. In fact, snow is white because it is reflecting all of the visible solar radiation. An absence of snow allows the dark ground to absorb sunlight, warming the ground and then the air near the ground.