According to Wikipedia:
“Groundhog Day is a holiday celebrated on February 2 in the UnitedGroundhog emerges from its burrow on this day, it will leave the burrow, signifying that winter will soon end. If on the other hand, it is sunny, the groundhog will supposedly "see its shadow" and retreat back into its burrow, and winter will continue for six more weeks. ”
read more at http://en.wikipedia.org
The largest Groundhog Day celebration is held in Punxsutawney, Pennsylvania and Groundhog Day is well known because of the 1993 film Groundhog Day, set in Punxsutawney and featuring “Punxsutawney Phil”, a Groundhog who lives there.
There is also a “History of Groundhog Day at life123.com/holidays