The rodent at the center of Groundhog Day is the groundhog, also called a woodchuck. The tradition says that if it emerges on February 2 and sees its shadow, winter will last six more weeks; if not, spring will arrive early.
The custom developed from German-speaking weather lore associated with Candlemas. In Germany, a badger traditionally served as the forecasting animal, but Pennsylvania German communities adapted the story to the locally familiar groundhog. The earliest recorded Pennsylvania observance dates to 1840, while Punxsutawney’s famous ceremony began in the 1880s.
Punxsutawney Phil is the best-known groundhog prognosticator, though many towns hold their own ceremonies. The prediction is folklore rather than reliable meteorology: studies have found no consistent relationship between a groundhog’s shadow and the timing of spring weather. Groundhogs themselves are large marmots and genuine hibernators.