The preliminary look from the National Weather Service for May is out. It was chilly, in the lowest quartile of historic temperatures for May in Flagstaff.
From the graph below, you can see that the beautiful days were just barely above average, but the cold, wet days were way below average. Many days were 4-6 degrees below average. Three days were 13 or 14 degrees below average.
While a few warm days are ahead, the temperature profile for the next few weeks continues to have periods with temperatures below normal, too.