Groundhog Day is a holiday celebrated on February 2nd in the United States and Canada. According to folklore, if it is cloudy when a groundhog emerges from its burrow on this day, it will leave the burrow, signifying that winter-like weather will soon end. If it is sunny, the groundhog will supposedly see its shadow and retreat back into its burrow, and the winter weather will continue for six more weeks.

http://en.wikipedia.org/wiki/Groundhog_Day