This rhyme is told on Groundhog Day, on February 2nd each year. Groundhog Day, the popular American holiday, has its roots in the European holiday Candlemas. Both recognize that it's the halfway point of Winter.
If the groundhog sees his shadow
We will have six more weeks of Winter.
If he doesn't see his shadow,
We will have an early Spring.
You can read more about Groundhog Day on Mama Lisa's World Blog.
Thanks and Acknowledgements
Many thanks to Jason Pomerantz for reciting this rhyme for us!