The Celtic — and magical! — festival of Imbolc, celebrated February 1-2, was considered the first day of spring in Celtic cultures and across Europe in general during the medieval period. Although we nowadays generally consider the solstice or equinox the first day of a season (December 21 as the first day of winter, March 21 as the first day of spring, June 21 as the first day of summer, and September 21 as the beginning of autumn), those days were previously considered the mid-seasons. (That is why we can sing Christmas carols about “midwinter” in December and have Midsummer night dreams in June!) The traditional changes of the seasons were the “quarter days” which marked the midpoints between the mid-seasons. So we get the Celtic/magical festivals of Samhain (October 31, the first day of winter), Imbolc (February 1-2, the beginning of spring), Beltane (May, the first day of summer), and Lammas (August 1, the beginning of autumn).
Because Imbolc is the beginning of spring, it is often associated with various means of predicting the coming weather which is so crucial during the planting season of agricultural societies. Hence, we consult the groundhog to determine if he sees his shadow or not in order to know if cold and snow will last another six weeks or not. In Serbia, a bear who wakes from his hibernation to stumble out of his cave and see his shadow will know whether to go back to sleep for another six weeks or not, based on whether he sees his shadow. Imbolc was believed to be when the Cailleach—the divine hag of Gaelic tradition—gathers her firewood for the rest of the winter. Legend has it that if she wishes to make the winter last a good while longer, she will make sure the weather on Imbolc is bright and sunny, so she can gather plenty of firewood. Therefore, people would be relieved if Imbolc is a day of foul weather, as it means the Cailleach is asleep and winter is almost over. At Imbolc on the Isle of Man, where she is known as Caillagh ny Groamagh, the Cailleach is said to take the form of a gigantic bird carrying sticks in her beak.