May 2013 will be noted as one of the gloomier months of May in the Twin Cities looking back to 1963.
As of May 29, the solar radiation measurements at the University of Minnesota St. Paul Campus Climate Observatory show that May 2013 is the third gloomiest May since 1963. The gloomiest May 1-29 is 2005.
Memorial Day Weekend wasn't the bright spot of the month either. From a climatological perspective, the 2013 Memorial Day weekend ranked the third lowest for solar radiation since 1971 with the year 2000 coming in as the lowest. For memorial day itself, 1971 was the only year that had significantly less sunshine than this year.
The blame for the cool and gloomy May is on a jet stream that allowed a series of low pressure systems to move over the region, some of which stalled and prolonged the clouds. While there were a few sunny days in May, there's been measurable rain on 16 of 29 days. So far at the Twin Cities International Airport 5.96 inches of rain has fallen so far this month, not enough to make it into the top 15 wettest Mays, but still well above average.