A Blue Norther, also known as a Texas Norther, is a fast moving cold front in the plains area of the U.S. Midwest, marked by a sudden drop in temperature, heavy precipitation, and dark blue skies moving rapidly. The phrase originated within Texas, where the land is very flat, perhaps making the approaching front seem darker and more threatening. The cold front originates from the north, hence the "norther,". The interaction between the warm causing cool temperatures and precipitation.
Because the Midwest lies to the north of the Gulf of Mexico and to the east of the Rocky Mountains in the zone of the westerlies during the winter, temperatures can closely follow the sun, and highs that precede a Texas norther can, reach 85 °F in January and 90 °F under bright sunlight in nearly-calm conditions before the cold front passes through. Winds turn sharply from the north and become very strong. Windchill due to a combination of cold temperatures and strong winds is dangerous to anyone who is caught unaware and unprepared for it. It exists only from November to early March in Texas
This phenomenon is rare but is most common in November, when the last vestiges of fall are still clinging on. One of the most famous Blue Northers was the Great Blue Norther of November 11, 1911, which spawned tornadoes and dropped temperatures 40 degrees in only 15 minutes and 67 degrees in 10 hours, a world record.