OK. This morning Punxsutaweny Phil, the nation's original weatherman, saw his shadow, indicating "six more weeks of winter". Think this through:
When you see shadows, it is a bright, sunny day. If you don't see shadows, it is cloudy and overcast. So, "sunny" equals more winter? What's with that?
February 2 is a middle point between Winter Solstice on December 21 and Spring Equinox on March 20. (Note to enquiring minds: Soltices and Equinoxes do NOT occur on the same date each year due to the nature of the Earth's orbit around the Sun. More here. And here.)
And forklore has it that if the midpoint of Winter is bright and sunny, the remaining weeks of Winter will be harsh and stormy. So ... Seeing a shadow on February 2 equals "bright and sunny" which equals more more harsh Winter weather to come. More here.
So, it is NOT that the critter himself makes the weather prediction ... its whether or not it is sunny enough for the critter to cast a shadow.
February 2 is also exactly 40 days after December 25. Ancient Jewish women celebrated a ritual purification exactly 40 days after the birth of a son. Mary, the mother of Jesus, would have celebrated this ritual on February 2, 40 days after December 25. More here.