How good are the groundhog predictions?

Jimmy the Groundhog bites the ear of Sun Prairie Mayor Jon Freund on Groundhog Day 2015!


For well over 100 years, the emergence of the groundhog in early February has stirred the imaginations of shivering, winter-stressed humans across the United States.

Of course, no reasonable person harbors the expectation a rodent could best a human in any contest of meteorological skill.

The forecast made on Groundhog Day is an example of predicting the weather based on folklore. If the groundhog comes out of its hole and sees its shadow, we are in store for 40 more days of winter. Of course, after Feb. 2, there are only 47 days left of astronomical winter – which ends on or about March 21.

The predictions are correct about 40 percent of the time – vastly inferior to what is delivered by modern science.

Long before computers, the Weather Channel and the internet, humans needed weather forecasts. Farmers and sailors particularly needed to know if storms were approaching.

Over time, various folklore forecasts, often in the form of short rhymes, were devised and passed down through the generations. Though memorable, the folklore forecasts are of uneven quality — some good, others bad.

The roots of Groundhog Day go back to the sixth century. Feb. 2 is 40 days after Christmas and is known as Candlemas. On this day, candles that are used for the rest of the year are blessed. This is also about the midpoint in winter in meteorological, not astronomical, terms.

The forecast rhyme goes:

If Candlemas Day is bright and clear
There’ll be two winters in that year;
But if Candlemas Day is mild or brings rain,
Winter is gone and will not come again.

Of course, the weather conditions on Feb. 2 at single locations like Punxsutawney, Pennsylvania, or Sun Prairie tells us very little about the weather for the rest of the winter season. Right or wrong, they are fun community celebrations.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.

Category: Meteorology

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