February 2 marks the midway point between the winter solstice and the vernal equinox. In an alternative way of measuring time, February 2 marks the beginning of spring. The March 21st equinox is the climax of spring.
In some pre-Christian European cultures, especially in Germany, there was a custom of watching the badger come out of hibernation on the first of February to inspect the weather. The good Christian missionaries on advice from Pope Gregory I did not crush this myth but instead they subverted it and consecrated the day to Christ. The locals could watch the badger and worship Jesus all on the same day. Smart Pope.
In North America, the natives had a similar myth. But instead of the badger it was the bear. It is interesting that this same concept evolved in two entirely different cultures. Many peoples perceive, perhaps correctly, that animals have a special sense about the weather.
Our current custom was brought to the United States by English and Germans settlers. They changed the badger into the groundhog and presto! -- a new holiday. One of the very first celebrations occurred in Pennsylvania Dutch (really Deutch, for German) settlements of Lancaster County in 1887. The town now closely associated with Groundhog Day is Punxsutawney, Pennsylvania.
The popularity of His Majesty, the Punxsutawney groundhog, has swelled enormously. Reporters, radio disc jockeys and television personalities descend upon the town and its chief citizen. Every February 2, His Majesty emerges from his burrow, if he sees his shadow there will be six more weeks of winter weather. But if it is cloudy he will return to his burrow for a long sleep and there will be an early and mild spring.