According to legend, if it is cloudy when a groundhog emerges from its burrow on February 2, he will leave the burrow -- signaling that cold winter weather will soon end, bringing an early spring. If it is sunny and the groundhog sees its shadow, he will return to his burrow and winter will last for approximately six more weeks.
See more about the origin of the Groundhog Day legend and some fun facts about Punxsutawney Phil, below.
The holiday is rooted in German superstition surrounding the tradition of Candlemas Day, the midpoint between the Winter Solstice and the Spring Equinox. When German settlers arrived in Pennsylvania in the 18th century, they brought the tradition of Candlemas with them. The tradition is celebrated on February 2, and according to an old English song:
If Candlemas be fair and bright, Come, Winter, have another flight; If Candlemas brings clouds and rain, Go Winter, and come not again.