The Old Farmer’s Almanac publishes a compendium of folklore and the bits of science that make each myth possible. One such bit of science concerns how the groundhog’s prediction of the six weeks of weather following Feb. 2 is actually partly dependent on the weather phenomenon called El Niño.
El Niño is an abnormally warm tropical Pacific current that usually produces a warm winter starting along the West Coast and moving east. In El Niño years, the East can have a very cool early winter, and then a warm mid-winter as the current arrives, followed by a return to cold for the remainder of the winter when the current dissipates.
If Punxsutawney Phil (or your local groundhog) is out and about on a relatively warm Feb. 2, and the sun is out, it most definitely could happen to see its shadow. If it’s an El Niño year, the warm spell will be followed by return to cold, so it will seem that seeing its shadow was related to the return of more typical cold winter weather. Thus developed the folklore based on the groundhog seeing its shadow meaning six more weeks of cold temperatures; if it doesn’t see its shadow, “winter will melt away,” according to the Almanac.
This folklore began in medieval times in Europe. People watched hedgehogs, badgers, bears or wolves to see if they saw their shadows on Feb. 2, which was Candlemas Day, a religious holiday. The settlers in America chose the groundhog to be its prognosticator.
The National Climate Data Center has kept track of the groundhog’s accuracy. Since 1988, it has been correct only 39 percent of the time—but we do love our traditions!