it makes no sense to me.
If the groundhog sees his shadow, presumably because it's not cloudy and dark (i.e. sun?), he gets scared and runs back in his burrow indicating it will be another 6 weeks of winter.
If it's cloudy and dark and he doesn't see his shadow he hangs out in the dank weather and calls it Spring.
Silly groundhog. Shouldn't the opposite be true?