Back in 1557, a man by the name of Thomas Tusser compiled a book called "A Hundred Good Points of Husbandry".  In April's husbandry (the cultivation or production of edible crops or of animals for food; agriculture; farming), he included this saying:

Sweet April showers Do spring May flowers.

This quote has prompted many poems, but one of my favorites is in the form of a song, "April Showers", first introduced by Al Jolson in the Broadway musical Bombo, written by Louis Silvers (music) and B.G. De Sylva (lyrics).

(I have added pictures from my recent trip to Salt Lake City.)

 
April Showers

Life is not a highway strewn with flowers,
Still it holds a goodly share of bliss,
When the sun gives way to April showers,
Here is the point you should never miss.

 
Though April showers may come your way,
They bring the flowers that bloom in May.
 
So if it's raining, have no regrets,

 
Because it isn't raining rain, you know,

 
(It's raining violets,)
And where you see clouds upon the hills,
 
You soon will see crowds of daffodils,
 
So keep on looking for a blue bird, And list'ning for his song,
Whenever April showers come along.
 
And where you see clouds upon the hills,
 
You soon will see crowds of daffodils,
So keep on looking for a blue bird, And list'ning for his song,
Whenever April showers come along.

 
For you listening pleasure, here are some YouTube links to different versions of the song!  Welcome May flowers!

April Showers with Al Jolson

Judy Garland sings April Showers

April Showers sung by Mel Torme