Groundhog Day is coming! Will the groundhog see his shadow? If we were in the middle of an El Niño, he might just see it. Behind the rodent folklore is an odd bit of science trivia.
The Folklore—Look at the legend that has had folks trekking to Punxsutawney, Pennsylvania since 1887. According to the folklore, if Phil the groundhog comes out of his hole and sees his shadow on February 2, it means there will be six more weeks of really crummy weather. If not, the rest of winter will melt away.
This legend is a holdover from European folklore. Since medieval times, people watched hedgehogs, badgers, bears or wolves to see if they saw their shadows on Candlemas, February 2. Once people settled in America, the local groundhogs took the place of bears, badgers and other critters.
According to the National Climate Data Center (NCDC), the tradition became publicized in 1887 when a newspaperman wrote about local hunters who celebrated February 2 by going on a groundhog hunt, followed by a jolly groundhog barbecue. He embellished the story with tales of the forecasting skills of Punxsutawney Phil. The rest is history.
The Science—When people continue a weather tradition, it is usually because it contains at least a small grain of truth. Historically the grain of truth for Groundhog’s Day in America is related to the El Niño.
The El Niño, an abnormally warm Tropical Pacific current, warps global wind and weather patterns. In North America it usually produces a warm winter starting along the West Coast and expanding eastward. By mid-winter, the warmth of a moderate to large El Niño usually reaches the Great Lakes and Midwest. Then, as the El Niño weakens, the warmth retreats and normal winter returns to the East.
In large parts of the East, this means an El Niño frequently produces a cool early winter, warm mid-winter and cool late winter. If a large rodent was wandering around in the relatively mild mid-winter, there might be enough sunshine to see his shadow. Then the El Niño would weaken and winter would literally come storming back.
It should be remembered that the Groundhog tradition persisted in America during the 1700s and 1800s, during the last stages of the “Little Ice Age.” What occasionally worked during those chilly times may not work now. The NCDC claims that since 1988, groundhogs have only had a 39% accuracy rate.
Accurate or not—it’s a great holiday and a good excuse for a party or barbecue.
Is the weather mild enough that a groundhog would see his shadow in your area? Do you think the rest of winter will be harsh or will it finally ease up?
Evelyn Browning Garriss, historical climatologist, is a longtime writer for The Old Farmer's Almanac. She is also editor of The Browning World Climate Bulletin  and has advised farmers, businesses, and investors worldwide on upcoming climate events and their economic and social impact for the past 21 years.