Why Do We Celebrate Snow at Christmas?

My post from last year. We had a snowy December, but the temps have risen to the forties and though snow remains, it is the patchy, gray, dirty kind. I think the temps are to fall again. Why snow at Christmas? We celebrate snow, it appears sometimes. What does the snow mean?

 As the low milky sun visits my window in the fifty degree weather, I'm amazed every year at how people marvel at the mild weather. I want to scream, "It's still fall in early December." Winter will come. It always does in the North. Maybe not as wild as some years, but we have a change in seasons. The winter solstice remains on December 20 or 21, depending on the timing of all that solar stuff.
December of 2001, the forsythia bloomed. Last year and the year before, I saw violets in October and late November. The year Mary Ellen was born, 1994, an extremely warm December, made it difficult to dress a newborn. I felt guilty not bundling her up, but we saw seventy degrees on Christmas Day. I wore a red light weight skirt and a white and red blouse, but it didn't look Christmas-like to me. I still felt warm, thank you, hormones.
Some years, I have seen snow start in October and early November. Two years ago, snow came before Thanksgiving and we didn't seen bare ground until April. Then it was muddy through June because of all the rain. Fifty days out of sixty one in April and May of rain. Now, that was depressing.
So why do we think we have to have snow and cold for Christmas? Folk lore, Washington Irving, Charles Dickens, Clement Clarke Moore, Santa living at the North Pole? Or is it my idea about the magic of first snow, that symbolizes cleaning the earth. Our sins will be cleansed by the blood of this Baby born on Christmas Day. I don't think we realize this consciously, but in our spirits we are open to a new start, being a new creation. Is that why we want snow at Christmas? Why we are disappointed when no snow shows on December first? We're ready for purity, the innocence of Christmas. Jesus said,"Unless you change and become like little children, you will not enter the Kingdom of Heaven." Mathew 18:3.