Slow Spring: Degree Day Maps

I recently read a MSU Extension article called "Looking at growing degree days: Just how far behind normal are we?".  The article includes maps of Michigan showing the amount of heat accumulation (measured as degree days) so far this spring. In terms of degree days, Michigan is 2 to 3 weeks behind this spring compared to the average year. Last year at this time, we were actually 2+ weeks ahead...shows how variable northern climates can be from  year to year.