|Max rating1||F4 tornado|
|1Most severe tornado damage; see Fujita scale|
The Great Blue Norther of November 11, 1911 was a cold snap that affected the central United States on Saturday, November 11, 1911. Many cities broke record highs, going into the 70s and 80s early that afternoon. By nightfall, cities were dealing with temperatures in the teens and single-digits on the Fahrenheit scale. This is the only day in many midwest cities' weather bureau jurisdictions where the record highs and lows were broken for the same day. Some cities experienced tornadoes on Saturday and a blizzard on Sunday.  A blizzard even occurred within one hour after an F4 tornado hit Rock County, Wisconsin.
The main cause of such a dramatic cold snap 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, though they can also come in February or March.  These arrivals of Continental Polar or Arctic air masses are generally called northers,   and the one in question was marked by a mass of steel blue clouds in the vicinity of the surface front, hence the name.  Although temperature drops of this extent have happened on other occasions, as recently as February 2009, the fact that the 1911 cold front passage was during the autumn and came after such warm weather contributed to the properties mentioned in this article. 
Temperatures in Kansas City had reached a record high of 76° F (24 °C) 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 (−11.7 °C), a 65 Fahrenheit degree (35 Celsius degree) difference in 14 hours. 
In Springfield, the temperature difference was even more extreme. Springfield was at 80 °F (27 °C) at about 3:45 PM, before the cold front moved through. Fifteen minutes later, the temperature was at 40 °F (4 °C) with winds blasting out of the northwest at 40 mph (64 km/h). By 7:00 P.M. Central Standard Time (01:00 UTC 12 November) the temperature had dropped a further 20 °F (3.9 °C), and by midnight, a record low of 13 °F (−11 °C) 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 °F (37 °C) in 10 hours. 
Record highs and lows were established on the same day in Oklahoma City as well with a high of 83 °F (28 °C) and low of 17 °F (−8 °C); temperature difference: 66 °F (36 °C). Both records still hold to this day. 
Alongside the dramatic temperature swings, the cold front brought a destructive tornado outbreak to parts of the Midwest. At least nine tornadoes touched down across five states as the system moved through, resulting in 13 fatalities. Hundreds of structures were destroyed by the storms and many areas had to conduct search and rescue missions amidst blizzard conditions. According to Thomas P. Grazulis, this outbreak was one of the worst on record in November for the north-central States. 
|List of reported tornadoes – Saturday, November 11, 1911|
|F2||W of Davenport||Scott||12:55 p.m.||9 miles (14 km)||The first known tornado of the outbreak touched down 1 mi (1.6 km) west of Davenport and tracked northeast. Along its path, five farms sustained damage and a barn was destroyed. One person was injured by the tornado. |
|F2||Virginia area||Cass||4:00 p.m.||18 miles (29 km)||Tornado touched down near Arenzville and tracked northeast into the town of Virginia. There, about 100 structures were damaged or destroyed. The worst damage occurred on the west side of town where 30 homes and businesses, including a church and high school, were destroyed. Overall, 18 people were injured by the tornado and losses reached $150,000. |
|F3||S of Easton||Mason||4:45 p.m.||11 miles (18 km)||2 deaths – A strong tornado touched down south of Easton and destroyed several homes. Two people were killed in separate incidents near the town. Nine other people were injured by the tornado and losses reached $20,000. |
|F2||E of Aurora||DuPage||5:30 p.m.||4 miles (6.4 km)||A tornado touched down east of Aurora and damaged several buildings. One home lost its roof and another was struck by debris from a barn. The tornado was last noted moving into the "big woods" northeast of Aurora. Losses from the storm reached $10,000. |
|F?||Unknown||Cass||Unknown||Unknown||A study in 1993 chronicling all tornadoes in Illinois prior to 1916 revealed that a tornado touched down in Cass County and injured 12 people. |
|F?||Unknown||Kankakee||Unknown||Unknown||A study in 1993 chronicling all tornadoes in Illinois prior to 1916 revealed that a tornado touched down in Kankakee County. |
|F?||Unknown||Cumberland||Unknown||Unknown||A study in 1993 chronicling all tornadoes in Illinois prior to 1916 revealed that a tornado touched down in Cumberland County. |
|F3||Leroy to S of Michigan City||Lake, Porter||7:00 p.m.||30 miles (48 km)||A strong, long-lived tornado first touched down near Leroy and tracked northeast to Michigan City. The most significant damage took pace near Lake Eliza where a school was destroyed. Debris from the building was tossed up to 2 mi (3.2 km) away. Another school in Jackson Township was also destroyed. Along the tornado's path, buildings were destroyed on 15 farms. One person was picked up and tossed to his neighbor's house by the storm. According to Thomas P. Grazulis, this tornado was likely a tornado family and not a single, continuous event. |
|F?||Terre Haute area||Vigo||9:10 p.m.||≥0.5 miles (0.80 km)||Apparent tornado struck Terre Haute and injured three people. Touching down in the heart of the town, the tornado soon struck a grocery store, blowing out lights and windows. Several barns along the tornado's path were completely destroyed or flattened. One home in the city was flattened and swept clean off its foundation, leaving just an underground cellar behind. The second floor of the John Rankin School was destroyed. The caboose of a train in the town was thrown off the tracks, injuring the occupants. |
|F2||Waterloo area||DeKalb||10:00 p.m.||5 miles (8.0 km)||A significant tornado struck the town of Waterloo, damaging or destroying at least 100 structures. An opera house in Waterloo collapsed due to the tornado. Just outside town, several farms were also severely damaged. Losses from the storm reached $75,000. |
|F?||Bedford area||Lawrence||~10:00 p.m.||Unknown||A possible tornado caused extensive damage in Bedford, with losses reaching $500,000. This may have been the same tornado that struck Waterloo. |
|F4||SW of Janesville to N of Milton||Rock||8:00 p.m.||18 miles (29 km)||9 deaths – The most powerful tornado of the outbreak caused extensive damage to Rock County, WI. Beginning at 2:00 pm, a tornado traveled north-northeast from the Town of Avon, and through the community of Hanover. The tornado skirted the northwest edge of Janesville, and then passed between Milton and Milton Junction, to a point in the Town of Lima, 4 miles northeast of Milton. The tornado finally dissipating in the extreme northeast corner of Rock County. Nearly $1 million in damage was reported. The worst damage occurred near Orfordville and near Milton.. Several farms were also leveled near Milton. The ninth fatality took place in this area. Overall losses from the tornado reached $1,000,000.  |
|F2||SE of Battle Creek||Calhoun||10:00 p.m.||Unknown||Tornado touched down well to the southeast of Battle Creek. Several barns were leveled and homes were damaged. |
|F?||Kingsland area||Eaton||~10:00 p.m.||Unknown||Possible tornado killed horses and cattle. |
|F2||Laingsburg to Owosso||Shiawassee||11:05 p.m.||12 miles (19 km)||2 deaths – Extensive damage took place in Laingsburg. Five factories and twenty homes were destroyed. Two people were killed when the upper floor of their home collapsed on them. Twenty-one people were injured throughout the town. Just outside Laingsburg, 15 barns were destroyed by the tornado. Overall losses from the storm reached $500,000. |
- Grazulis, Thomas P. (November 1990). Significant Tornadoes 1880–1989. 2. St. Johnsbury, Vermont: The Tornado Project of Environmental Films. ISBN 1-879362-02-3.
- "Waterloo Swept By Cyclone; Cutting Swath Through the Business Section of Town". The Fort Wayne Journal Gazette. Nov 12, 1911. Archived from the original on September 30, 2011. Retrieved November 11, 2011.
- Albert, Drew (October 2003). "The Great "Blue Norther" of November 11, 1911". Ozarks Weather Observer. Retrieved November 11, 2011.
- "The Great Blue Norther of November 11, 1911". National Weather Service Weather Forecast Office - Norman, Oklahoma. National Oceanic and Atmospheric Administration. March 12, 2014. Retrieved May 17, 2014.
- Grazulis, p. 125
- Grazulis, p. 124
- Wayne M. Wendland and Herbert Hoffman (1993). "Illinois Tornadoes Prior to 1916" (PDF). Transactions of the Illinois State Academy of Science. 86 (1): 7. Archived from the original ( PDF) on October 8, 2011. Retrieved March 18, 2012.
- Mike McCormick (December 25, 2011). "Historical Perspective: November 1911 tornado causes havoc in city, county". Tribune Star. Retrieved March 18, 2012.