They believed that if the animals saw their shadows, winter would continue, and so they went back to sleep.

CNN: Shadows aren't just for groundhogs

If the animals saw their shadows, winter would go on for another six weeks, and they could go back to sleep, according to the tradition.

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Winter, city life (with the concomitant shadows cast by tall buildings) and dark skin in dark climates all reduce this action.

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In honor of this quirky American tradition, CNN iReport is asking people to take a snapshot of their own shadows for a one-day photo challenge and share their own winter weather predictions.

CNN: Shadows aren't just for groundhogs