Christmas signs and weather warnings
Many people in the old farming community took weather forecasts, and it was especially good to take forecasts on holidays. During the twelve days of Christmas, people could see what the weather would be like in the coming year – important knowledge, especially in relation to field work.
Christian IV made Christmas marks for some of the days of Christmas in his written calendar from 1614, but otherwise it is part of folk belief. The farmer drew twelve circles on a ceiling beam in his house, and here he could keep an annual calendar of the weather. He noted the weather in a circle every day during the twelve holy days of Christmas, and thus the weather would be the following year.
The tradition disappears during the 19th century, but in 1804 the book 'Farmer internship or Weather book from which one can know the constant course and weather of the entire year, from year to year.' published with an explanation of how to take Christmas stamps. As a curiosity, it should be highlighted that it is written in verse and with rhyme.
BUT… what is extra interesting is that for the next six days (i.e. after the twelve holy days of Christmas) you can also take notices – they are also called “anniversaries”
The book states the following (for those who are good at reading Gothic script):

From Farmer Internship.
This means that you have extra 'insurance' here. The six days have two months in them – the morning weather shows one month and the afternoon weather shows the next month.
This means that you either reinforce a Christmas sign from the first twelve days (because the weather shows the same, so it must be that way), or you get an explanation here as to why a Christmas sign does not hold true when you now get to the month in question. Because the weather from the six days of the holiday did not match that from the twelve days of Christmas, so one sign was right.
A kind of safety valve, so that folk beliefs could fit reality.
And did the weather now become something completely different than what both marks for the same month otherwise showed? Yes, then it was probably the underground that had a hand in the game; Or one of the many other creatures from folk belief. This gave one more safety valve/explanation option, so that the folk belief fit and was not rejected. After all, it was important to be able to explain and understand all the inexplicable and incomprehensible.
