Temperatures in the 50s in the Red River Valley during February are rare, but not unknown. Such weather invariably occurs when there is very little snow cover. There have only been three times since records began in 1881 that Fargo Moorhead has had more than two February days in the 50s. This happened most recently in 2017. On February 17, the temperature hit 53 degrees. Two days later, it was 56 degrees. The following day, for good measure, it was 54. Back in 1905, there were also three days in the 50s.
The record is five February days in the 50s. It happened in 1958 and included the February record of 66 degrees set February 25. Since 1881, there have been 3,889 February days, and just 41 of them have been 50 degrees or warmer. So the probability of any single February day getting to 50 degrees has been about 1%.