The last frost of spring is a weather element that is highly variable from year to year. For the next week, record lows for Fargo range from 17 degrees to 22 degrees. Record lows from the northern valley and northwestern Minnesota are even colder, suggesting that a hard freeze or two is certainly possible statistically.
Just like a snow that falls after the winter snow has melted away, a frost or freeze that happens after lawns have greened up seems out of place. It requires an attitude adjustment and might require a little extra work of anyone who has set out annual plants already. However, a look back at past years indicates how often cold weather has occurred at this point in May. Fargo's latest freeze on record is June 20, 1969, when it was 30 degrees.