(I actually found this link under Weather, but felt it would be misleading to use that as the subject.)
There is more to Groundhog Day than meets the eye! The name came from the Delaware Indians, but the tradition is based on the German Candlemas Day.
http://weather.about.com/gi/dynamic/offsite.htm?site=http://www.stormfax.com/ghogday.htm

For the early Christians in Europe, it was the custom on Candlemas Day for clergy to bless candles and distribute them to the people in the dark of Winter. A lighted candle was placed in each window of the home. The day's weather continued to be important. If the sun came out February 2, halfway between Winter and Spring, it meant six more weeks of wintry weather.

And then that damned groundhog came along and bogarted the holiday, huh? Well, they should've known he was after a movie contract in the first place.

And, actually, everything from the Candlemas but the Feb. 2 tradition of ascertaining the longevity of Winter, was infused into the Dec. 25 celebration of Christmas, which the first early Roman Christian emperors moved to that date because it was in harmony with the feast of Saturnalia, and helped to spread the Word to their constituents in a more familiar manner. That's where all the candles come from as part of the Christmas imagery. And, of course, the light shining in the darkness (in the depth of Winter) is a feast and ritual going back to ancient pagan celebrations. The true birth of Christ is believed to be closer to the Julian calender's date of Jan. 7...and some even put it another month or two later.

(this is all off the top of my had, if some of it is a bit off, please feel free to correct me)

from the link:

If the sun shines on Groundhog Day,
Half the fuel and half the hay.

more like

If the sun shines on Groundhog Day,
Stoke the fuel and hit the hay!

and candlemas day is neatly timed to the irish holiday of February 1st, which marks the "death of winter' (May 1st, 3 months later is beginning of summer) spring is somewhere between the death of winter and the birth of summer....
as christianty came to ireland, Rome was falling.. and many pagan practices of the irish got sublimated into irish christianty. (just as roman practices did, "st Valentines day makes a pagan roman love feast that has became a christian (and then secular ) holiday.)

after the fall,(say 3 to 6 hundtred years (lets date the fall with the sacking of rome, what, 465?) irish priest and brothers (isolated from the war and destruction that was part of romes fall), came to mainland and brought back christian learning, and irish influences to christiany. (especially roman catholic christianty) No other culture (besides rome) had as much influence.

In rural places, it is also lambing time.. most lambs are born in the first week of February, (neatly timed to make spring lamb in six weeks!)