A 90 degree high temperature in May occur approximately every 3 years. Before this month, the most recent years with a high at 90 degrees or higher in Fargo Moorhead were back in 2010, 2006 and in 2001. Although temperatures that warm have occurred in only 46 Mays, everyday of the month, but one, has a record high of 90 degrees or higher. The exception is May 6 that has a record high of 88 degrees set back in 1896.
Although a few days in the 90s in May is not that usual, what has been historically rare has been temperatures in the triple digits. Since 1881 there has only been two recorded days when the high temperature reached 100 degrees or higher. By coincidence, both times were on May 30, one in 1934 and 1939. So if you have a 2012 StormTRACKER calendar you will notice only one record high this month above 100 degrees, a 104 degree high on May 30, 1934, but in 1939 there was another scorcher of 101 degrees on that very same day.