Groundhog Day is February 2, and is celebrated in Canada and the US. According to legend, the groundhog emerges from its burrow at noon on that day to look for its shadow. If it is a sunny day and the groundhog sees its shadow, according to folklore it becomes frightened and returns to its hole to sleep, and winter continues for 6 more weeks. If it does not see its shadow, it remains outside because the worst of winter is over and warmer weather is on its way.
The origins of Groundhog Day lie in medieval Europe, where the day was known as Candlemas Day, a Christian festival named for the custom of lighting candles on that day. There were sayings that carried the observations of the time of year in general. In Scotland, conventional wisdom said, "If Candlemas Day is bright and clear, There'll be twa [two] winters in the year." In England, the saying was somewhat more elaborate: "If Candlemas be fair and bright, Come, Winter, have another flight. If Candlemas brings clouds and rain, Go Winter, and come not again." In addition to being attentive to the changing seasons, Europeans may have had a legend whereby hedgehogs predicted the beginning of spring by the state of the weather on Candlemas Day. When European settlers came to North America, they brought the February 2 legend with them. There being no hedgehogs in North America, they transferred the predictive role to groundhogs.
Early settlers hoped for signs of an early spring so they could begin planting and shorten the time to harvest, especially with winter provisions dwindling. What settlers did not realize was that the groundhog sleeps later than the European hedgehog and is less likely to stir even on warm winter days. By February 2, the worst of winter's weather is usually over in western Europe, but Canadian winters are generally longer, with much more cold and snow yet to come. In early February, the openings to groundhog burrows are usually buried under deep layers of snow and ice.
There is some truth to the shadow aspect of the legend. Sunny days in winter are generally associated with colder, drier arctic air and cloudy days with milder, moist maritime air. Given the tendency for weather conditions to persist for several days before changing, the weather on any February 2 may continue for a few days, but not necessarily any longer. Since seasons tend to follow a pattern, 6 more weeks of winter, rather than an early spring, is a statistically better option in Canada.