Q: If April showers bring May flowers, what do May flowers bring?
A: Pilgrims!

Explanation: Happy Thanksgiving!!  This is one of my favorite jokes and one that I did not understand when I was a kid.

In the northern hemisphere spring comes around the month of April.  During April it rains in many areas.  The rain that falls in April gives water to the flowers that bloom in May; in much of the northern hemisphere there is snow during the winter and nothing blooms.

This joke sets up a pattern: April showers bring May flowers; May flowers bring… ?  The answer is Pilgrims who arrived in what is now Massachusetts in a boat; the name of the boat was the Mayflower.  The joke is funny because you expect an answer that begins with June, the next month according to the pattern.

Here is Charlie Brown celebrating Thanksgiving: