Editor's Note: This morning (Feb. 2), at sunrise in Pennsylvania, the famous groundhog Punxsutawney Phil did not see his shadow, indicating that an early spring is on its way. 

Wednesday morning, groundhogs around the country will be prodded or pulled from their burrows to determine the prospects for spring in a celebration that has grown from an unlikely mixture of ancient tradition, marmot biology and good old-fashioned promotion.

The modern Groundhog Day has its origins in the Old World with an ancient celebration of the midpoint between the winter solstice and spring Equinox. This became the Christian celebration of Candlemas on Feb. 2 that celebrates the presentation of the Christ child and Mary's ritual purification, but pagan folklore associated with the changing season stuck, according to Stam Zervanos, a professor emeritus of biology at Pennsylvania State University, Berks College, who has studied groundhog hibernation.

German settlers brought folklore that associated the shadows of animals, including the hibernating hedgehog, with an extended winter, when they settled in Pennsylvania. Hedgehogs aren't native to North America, but groundhogs are. And they first emerge from their burrows in early February when hedgehogs do.

"They put two and two together, and instead of a hedgehog they used a groundhog," Zervanos said.

In southeastern Pennsylvania, where Zervanos studies the hibernation habits of groundhogs, the animals hibernate for an average of 104 days. However, they periodically awaken from their torpor.

Groundhog greeting

At the study site, they emerge for the first time, on average, on Feb. 4, two days after Groundhog Day. However, weather can change this.

"I was out Sunday walking around in the snow, and I didn't see that anybody has come out yet," he said.

After first emerging, the males start setting up territories, fending off other males and starting to bond with females. After a preliminary courtship, the groundhogs return to their burrows and continue hibernating until the mating season begins in March, he said.  

Harsh weather that has dumped record amounts of snow along the East Coast may delay the process this year. A significant delay could create a problem, because the young won't have time to put on enough weight to make it through the next winter, he said.

The modern Groundhog Day celebration originates in Punxsutawney, also in Pennsylvania, where in 1887, the editor of the local newspaper described a group of local hunters and gourmets known as the Punxsutawney Groundhog Club, who held a groundhog hunt followed by a barbecue. The editor went on to promote the Punxsutawney Groundhog as the official weather forecaster, according to the U.S. National Climatic Data Center.

The Center, however, cautions about putting too much stock in his predictions.

"It really isn't a 'bright' idea to take a measure such as a groundhog's shadow and use it as a predictive meteorological tool for the entire United States," it cautions on its website.

Zervanos puts the accuracy of the famous groundhog, Punxsutawney Phil, at 39 percent.

In parts of the country without groundhogs, other animals, including the semiaquatic invasive nutria, have been pulled into service.

You can follow LiveScience writer Wynne Parry on Twitter @Wynne_Parry.