If the groundhog sees its shadow Feb. 2, why does that mean six more weeks of winter?
Why, on Groundhog Day, if the groundhog sees its shadow, does it mean that there will be six more weeks of winter? Presumably if the weather was nice enough to see a shadow, winter would be over.
First we have to cleanse the problem of extraneous detail. This has nothing to do with groundhogs. In Europe the same legend has attached to bears, badgers, and hedgehogs. German immigrants brought it to North America in the 19th century and, not finding any hedgehogs, settled on the somewhat similar (it's small, it hibernates) woodchuck, AKA groundhog. Not that you need animals of any sort. Medieval English proverbs strip the proposition to its paradoxical core: "If Candlemas Day [also February 2] be bright and warm, ye may mend yer auld mittens and look for a storm." Some writers (e.g., Gail Cleere in Natural History) trace the belief back even further "to an ancient pagan celebration [by Scottish Celts] called Imbolog, which marked a `cross-quarter' day, one of the days that fall midway between the four mileposts of the solar year," namely the solstices and equinoxes.
Incredibly interesting, but why did people figure good weather today meant crappy weather later? Beats me, and from what I can tell, pretty much beats everybody else too. Best, or perhaps I should say only, theory: sunny days in winter are the product of cold, dry arctic air masses, while cloudy days result from mild, moist tropical air. Unfortunately, while this may be true as a general proposition, the predictive value of cloudy weather on February 2 pretty much sucks. 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.