Groundhog Day is a celebrated way to foretell the end of winter. According to folklore, if it is cloudy when a groundhog emerges from its burrow on this day, then the spring season will arrive early, some time before the vernal equinox. If it is sunny, the groundhog will supposedly see its shadow and retreat back into its den, and winter weather will persist for six more weeks.
Groundhog Day was adopted in the U.S. in 1887. Clymer H. Freas was the editor of the local paper Punxsutawney Spirit at the time, and he began promoting the town’s groundhog as the official “Groundhog Day meteorologist.”
Modern customs of the holiday involve an early morning festival held to watch the groundhog emerging from its burrow. The largest Groundhog Day celebration is held in Punxsutawney, Pennsylvania, where crowds as high as 40,000 have gathered to celebrate the holiday since at least 1886.
The holiday, which began as a Pennsylvania German custom in southeastern and central Pennsylvania in the 18th and 19th centuries, has its origins in ancient European weather lore, wherein a badger or sacred bear is the prognosticator as opposed to a groundhog. The holiday also bears some similarities to a Pagan festival and also involves weather prognostication.
Groundhog Day received worldwide attention as a result of the 1993 film of the same name, Groundhog Day, which was set in Punxsutawney (though filmed primarily in Woodstock, Illinois) and featured Punxsutawney Phil. (from: Wikipedia and www.cute-calendar.com)