The Sky This Week, 2012 January 31 – February 7 — Naval Oceanography Portal

[Groundhog Day is] from a tradition brought over to America by German immigrants. Loosely based on the old pagan celebration of Imbolc, it was believed that if a hibernating animal awoke and saw its shadow there would be six more weeks of winter. No shadow indicated an early spring. Imbolc and its derivatives mark one of the so-called "cross-quarter" days in the ancient seasonal calendar, marking the mid-point of astronomical winter. Halloween is another one of these cross-quarter days that are still widely observed here in the New World, continuing traditions that date back millennia in time.

The Sky This Week, 2012 January 31 – February 7 — Naval Oceanography Portal