Groundhog Day, in both the United States and Canada, day (February 2nd) on which the emergence of the groundhog (woodchuck) from its burrow is said to foretell the weather for the following six weeks. The beginning of February, which falls roughly halfway between both the Winter Solstice and the Spring Equinox, has long been a significant time of the year in many cultures. Among the Celts, for example, it was the time of Imbolc, observed in anticipation of the birth of farm animals and the planting of crops, and February 2nd is also the date of the Christian festival of Candlemas, also called the feast of the Purification of the Blessed Virgin. During the Middle Ages there arose the belief that animals such as both the badger and the bear interrupted their hibernation to appear on this day. If the day was sunny and the animal saw its shadow, six more weeks of winter weather remained. If, however, the day was cloudy, it was a sign that the weather during the following weeks would be mild, leading to an early spring. German immigrants to the United States carried the legend with them, and in Pennsylvania the groundhog came to be substituted for the badger.

Since 1887, an animal in Punxsutawney, in the west-central part of the state, has been the centre of a staged appearance each February 2nd. In what has become a media event, a groundhog designated Punxsutawney Phil is the centre of attention of both television weathermen and newspaper photographers. Although promoters of the local festival surrounding Punxsutawney Phil claim that the animals have never been wrong, an examination of the records indicates a correlation of less than 40 percent. (Whether a groundhog does or does not emerge is thought to be related to the amount of fat it was able to store before going into hibernation.) Canada has a number of groundhogs that serve as weather prognosticators, perhaps the best known being those portraying Wiarton Willie, a white-furred, pink-eyed creature that has appeared on the Bruce Peninsula, northwest of Toronto, since 1956.