Slimebeast:
According to Wikipedia (since I don't know off-hand):
"The groundhog is the largest sciurid in its geographical range, typically measuring 40 to 65 cm (17 to 26 in) long (including a 15 cm tail) and weighing 2 to 4 kg (4.5 to 9 lbs). In areas with fewer natural predators and large quantities of alfalfa, groundhogs can grow to 80 cm (32 in) and 14 kg (30 lb)."
As for Groundhog Day, it's not a widely celebrated holiday (February 2 will just be another day for me), but it is significant since it indicates how long the winter season will be. Plus, it even has its own movie, and it's a pretty good movie at that. The holiday is really only celebrated in the countries where groundhogs can be found, so just the U.S. and Canada.