Blue Norther

I read the following statement today: "I was taught... to urinate South when a blue Norther was coming through Dallas". What exactly is a 'blue Norther'? Here is the definition, from the Handbook of Texas Online (www.tsha.utexas.edu/handbook/online):

"The term blue norther denotes a weather phenomenon common to large areas of the world's temperate zones–a rapidly moving autumnal cold front that causes temperatures to drop quickly and that often brings with it precipitation followed by a period of blue skies and cold weather. What is peculiar to Texas is the term itself. The derivation of blue norther is unclear; at least three folk attributions exist. The term refers, some say, to a norther that sweeps "out of the Panhandle under a blue-black sky"–that is, to a cold front named for the appearance of its leading edge. Another account states that the term refers to the appearance of the sky after the front has blown through, as the mid-nineteenth-century variant "blew-tailed norther" illustrates. Yet another derives the term from the fact that one supposedly turns blue from the cold brought by the front."