The roots of the tradition can be traced back to the ancient Germanic festival of Candlemas, celebrated on February 2nd. This festival marked the midpoint between the winter solstice and the spring equinox, and it was believed that if the sun shone on this day, spring would come early.
The tradition of the "hedgehog" (which was later replaced by the groundhog) predicting the weather came from the German folklore associated with Candlemas. It was believed that if a hedgehog saw its shadow on Candlemas, it would retreat to its burrow and winter would continue for six more weeks.
The tradition was brought to the United States by German immigrants in the 18th and 19th centuries. The name "groundhog" was substituted for "hedgehog" because the groundhog was a more common animal in Pennsylvania, where the tradition became particularly popular.
The first recorded Groundhog Day celebration in the United States was in 1887 in Punxsutawney, Pennsylvania. The tradition has since become a popular annual event, with many towns and cities across the country hosting their own Groundhog Day celebrations.