Although now overshadowed on the revised liturgical calendar, Feburary 2 bore a weather folklore long before the shadowy groundhog. Farmers found the day a good time to make weather predictions, applying the theory that the rest of the winter would be the opposite of that on Candlemas. There is an old English song about this:
If Candlemas be fair and bright,
Come, Winter, have another flight;
If Candlemas bring clouds and rain,
Go, Winter, and come not again.
This means if the sun casts a shadow on Candlemas, you can expect more winter, but if there is no shadow, the end of winter is close at hand. If that sounds like the old groundhog story, it’s because this is where that story comes from, except that the one about the groundhog originated only about a hundred years ago.
Taken from The Catholic Source Book
James M. Hahn, Author 