Q: What happens when winter arrives?
A: Autumn leaves!
Explanation: In the northern hemisphere winter officially starts on December 21 (winter solstice, astronomical winter), but for many places in the north, it is already cold. Did you know that there is more than one way to mark the start of winter? Meteorologists, people who study the weather, talk about meteorological winter which starts on December 1. When talking about seasons, winter comes after fall; fall is also known as autumn.
In the autumn, leaves change colors and fall to the ground as the trees get ready for the winter, and the following spring. Autumn leaves are beautiful!
Leaves, though, has another meaning. When something leaves, it goes away. For example, the teacher leaves home to go to work, and the student leaves school to go home.
This joke is funny because it plays with two meanings of the word leaves: The tree has leaves that change colors in the autumn (autumn leaves), and autumn leaves, or goes away, so that winter can come.
Eric Clapton has a song called Autumn Leaves–
Explain the Joke 
what do you call a snowman in the heat?
water
please explain joke
autumn leaves isn’t a clapton song; it a WELL known jazz standard from the 40s&50s.
Thank you! Yes, it is a well known jazz standard, and I would have been more accurate to say what you said. I hope you enjoyed the Clapton version. For more information about the song, I found this: https://frenchmoments.eu/autumn-leaves-the-story-of-the-song/