Groundhog Day is a popular tradition celebrated in Canada and the United
States on February 2. It derives from the Pennsylvania Dutch superstition
that if a groundhog (Marmota monax), also called "woodchuck";  emerging
from its burrow on this day sees a shadow due to clear weather, it will
retreat to its den and winter will persist for six more weeks, and if it does
not see its shadow because of cloudiness, spring will arrive early.