In the South, an "old blue northern" is nothing more than a cold front. My favorite version of this song is the Tanya Tucker recording, in which the words are:

There is a young man that I know, he just turned twenty-one
He comes from down in southern Colorado,
Just out of the service and he's looking for his fun
Someday soon, I'm going with him someday soon.

My parents cannot stand him, 'cause he rides the rodeo,
My mama says that he will leave me crying,
But I would follow him right down the roughest road I know,
And someday soon, I'm going with him someday soon.

When he comes to call
My pa ain't got a good word to say.
I guess it's cause he was just as wild
In his younger days-

Blow you old blue northern, blow my love to me,
He's driving in tonight from California-
Well, he loves his darned old rodeo as much as he loves me,
But someday soon, I'm going with him someday soon!

The last two verses are repeated before the song ends.