The date of the average last freezing temperature in the spring for the entire period of record (1881 - present) in Fargo-Moorhead is May 13. In the past 30 years, the date has slid to May 8.
This shift toward fewer late-season frosts has two reasons. The obvious one is the warming climate, but the increasing heat island effect of our growing city is also partly responsible.
Over the last 30 years, the final frost of spring has happened during April seven times and in May 23 times, including the earliest final frost on record on April 17, 2007. The following year, the last frost was recorded on May 27, which illustrates just how varied and unpredictable this particular statistic can be.
The latest final spring frost on record was in 1969, when the temperature reached 30 degrees on June 20.