Groundhog Day is a tradition observed regionally in the United States and Canada on February 2 of every year. It derives from the Pennsylvania Dutch superstition that if a groundhog emerges from its burrow on this day and sees its shadow, it will retreat to its den, and winter will go on for six more weeks; if it does not see its shadow, spring will arrive early. The Groundhog Day ceremony held at Punxsutawney in western Pennsylvania, centering on a groundhog named Punxsutawney Phil, has become the most frequently attended ceremony.

Source: Wikipedia