Many old folk traditions to foretell the future became associated with the Twelve Days of Christmas. For instance, dreams during the Twelve Nights were believed to foreshadow events that would occur in the ensuing year. The weather (sun, wind, snow, rain) on the Twelve Days of Christmas was thought to predict the weather for each of the corresponding twelve months of the new year.
It was not just the country folk who believed in the predictive value of the Twelve Days: Tycho Brahe, a pioneering 16th-century astronomer, theorized that the configuration of the heavenly bodies could be used to forecast the weather in the coming months and meticulously recorded his observations during the Twelve Days of Christmas to test his theory. Although predicting weather by the Twelve Days is not a quaint relic in the Old Farmer's Almanac, this is not as far-fetched as it may seem - scientists today still study events in space to analyze their potential effects on our weather.
The Astronomical Observations: The Moon, 1711, by Donato Creti