The Great Blue Norther of 11/11/11 was the biggest cold snap in U.S. history. Many cities broke record highs early that afternoon. By nightfall, cities were dealing with single-digit temperatures in the Fahrenheit scale. This is the only day in many midwest cities' weather bureau jurisdictions where the record highs and lows were broken on the same day. Coincidentally, it occurred on a palindrome date: Saturday, November 11, 1911 or 11/11/11.

What caused the cold snap?

The main cause of such a dramatic cold snap was that there was an extremely strong storm system separating warm, humid air from frigid, arctic air. Dramatic cold snaps tend to occur mostly in the month of November; such cold snaps can also come in February or March, however.

Kansas City

Temperatures in Kansas City had reached a record high of 76° F by late morning before the front moved through. As the cold front approached, the winds increased turning from southeast to northwest. By midnight, the temperature had dropped to 11° F, an astonishing 65 degree difference in 14 hours.

Springfield

In Springfield, the temperature difference was even more extreme. Springfield was at 80° before the cold front moved through. Two hours later, the temperature was at 40° with winds blasting out of the northwest at 40 mph. By 7:00 P.M. the temperature had dropped a further 7°, and by midnight, a record low of 13° was established. It was the first time since records had been kept for Springfield when the record high and record low were broken in the same day. The freak temperature difference was also a record breaker: 67° in 10 hours.

Record highs and lows were established on the same day in Oklahoma City as well (High: 83°, Low: 17°; temperature difference: 66°) This record still holds to this day.

Freak Weather

The front produced severe weather and tornadoes across the upper Mississippi Valley, a blizzard in Ohio, and the windy conditions upon front passage caused a dust storm in Oklahoma. Nine tornadoes were reported in Michigan, Illinois, Indiana, and Wisconsin. An F4 tornado hit in Janesville, Wisconsin killing 9 and injuring 50. Within an hour of the tornado, survivors were working in blizzard conditions and near zero temperatures to rescue people trapped in debris.

Another Notable Cold Wave

The Great Lakes area has experienced a number of dramatic cold snaps, albeit none so dramatic as the 11/11/11 cold wave. In the early afternoon hours of February 11, 1999, many cities in the Great Lakes area saw temperatures soar to more than 70° for the first time ever in February. South Bend, Indiana reported a record high of 72° F. By 8:00 P.M., temperatures had plummeted to near freezing. The previous record high for February 11 in South Bend was only 46°, smashed by an astounding 26 degrees hotter.