April Showers

When I was in kindergarten we learned the different months of the year with a calender hung in the front of class. Each month a new sign with the month's name would be hung with a scene in the background. In June, it would be sunshine, for July it was the American Flag. Most of these made sense to me except April. Why was it "April Showers?" It rains all year around. And then "May flowers?" Flowers are around starting in April.
Then I moved to Chicago and realized a northern came up with all that. It has rained almost everyday since it became April and the flowers have only just started to bloom, and probably won't have completely bloomed until May. It's interesting. As I was walking the dogs in the rain and realized that, I also realized that many sayings and things are revolved around life in the northern part of the nation. April showers bring May flowers, White Christmas, etc.Perhaps this goes back to the north being industrialized first?
No idea, just an observation during my walk today.