Via The Straight Dope, the groundhog is wrong more than right.

According to Canadian Geographic weather columnist David Phillips, a multidecade, multicity study in Canada found that groundhog-driven predictions were right only 37 percent of the time. Which means, I guess, that you'd be right 63 percent of the time if you said good weather on 2/2 meant good weather ahead. But what kind of weather proverb would that make? If the choice is between right and catchy, catchy wins every time.