Because of a legend and a popular Hollywood movie, tomorrow morning many eyes will turn to Punxsutawney, PA where, awakened by local officials from his winter slumber, a groundhog named Phil will step into the opening moments of daylight. Supposedly if he sees his shadow, we'll have six more weeks of winter. If he doesn't, spring is around the corner.

Now obviously, you can't take Phil's forecast seriously because whether the sun appears tomorrow morning or not has no bearing on the weather for the next six weeks. But there is a little meteorology behind Groundhog Day. You see, Phil would probably wake up anyway naturally due to the cold. Let me explain.

When groundhogs hibernate, their body temperature drops to just a degree or two above the temperature of their burrow. But if that temperature falls to where the animal's tissues can freeze, the groundhog will wake up. Now typically, air temperatures bottom out in late January. But the groundhog's burrow is usually four to six feet below ground, and it takes a few extra weeks for the deep chill to penetrate down that far. And so the coldest time in the burrow is often in early February, right around Groundhog Day.

Thus, though Phil the groundhog is no weather forecaster, meteorology does play a role in determining when groundhogs might actually wake up on their own.

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