What is Groundhog Day and why does it fall on February 2?

On February 2, thousands gather at US' Gobbler's Knob to witness the annual Groundhog Day tradition, wherein Punxsutawney Phil predicts the weather. According to folklore, if Phil sees its shadow, winter will continue for six more weeks; if not, an early spring is expected. February 2, linked to Candlemas, marks the time people traditionally looked for signs of seasonal change.