Why do groundhogs become weather experts for a day?

Every Feb. 2, thousands of winter-weary folk look to groundhogs to see whether an early spring is on the horizon.

It's a tradition historians trace back to European agricultural life, marking the midpoint between the winter solstice and the spring equinox.

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It was German settlers in Gobbler's Knob, Pennsylvania, that first put Groundhog Day on the map.

Since then, tens of thousands of people have made an annual pilgrimage to see if the world's most famous groundhog, Punxsutawney Phil, sees his shadow or not.

As the legend goes, if the groundhog sees its shadow, it will return to its burrow for another six weeks of winter weather.

If it doesn't, an early spring is coming.

There are weather-predicting groundhogs in at least 28 U.S. States and Canadian provinces. But how accurate are they?

Lakehead University Professor Michael Rennie and his students crunched the numbers and published what is believed to be the most comprehensive evaluation of groundhog spring predictions to date.

"We collected data from as many groundhogs as had information available," Rennie said. "We made sure we were looking at actual groundhogs and not just a guy with a puppet. We evaluated whether they were correct."

Studying groundhog predictions from as far back as a century and as far south as Georgia, the team found the large rodents aren't very accurate.

"We found flipping a coin is just as good as groundhog prediction as to whether it will be an early spring," he said

Even if they're wrong half the time, there's always next year.