Tornadoes are among the most devastating and awesome local storms that occur on Earth. The United States has the dubious distinction of having the greatest frequency and the most severe tornadoes. Tornadoes have the power to lift railroad cars and sail them many yards through the air. The power of their winds can make deadly missiles of loose objects, including broken glass. Even pieces of straw have been found imbedded in trees and boards after a tornado.
During the winter months (December through February) tornado activity is concentrated in the southeast U.S. and along the Gulf Coast. As spring (March/May) progresses, tornado occurrence moves north and west across the central Mississippi and Ohio River Valleys. By summer (June/August) the potential threat of tornadoes has spread across the continental United States and Southern Canada. During autumn (September/November), tornadic activity gradually retreats to the south and southeast sections of the country and is often associated with hurricanes.
This seasonal drift is principally caused by the increase of warm, Gulf moisture into the central part of the country during spring and summer, decreasing during the fall and winter. The mixing which occurs when the moist Gulf air clashes with contrasting colder, drier air from the north and northwest contributes to the triggering of tornadoes.
Minnesota lies along the north edge of the region of maximum tornado occurrence in the United States. Tornado Alley, as that part of the central U.S. has come to be known, reaches across parts of Texas, Oklahoma, Kansas, Missouri, East Nebraska, and West Iowa.
In Minnesota, tornadoes have occurred in every month from March through November. The earliest verified tornado in Minnesota occurred on March 18, 1968, north of Truman, and the latest in any year on November 16, 1931, east of Maple Plain. Historically and statistically, June is the month of greatest frequency with July not far behind. May has the third greatest frequency, followed closely by August. Nearly three-quarters of all tornadoes in Minnesota have occurred during the three months of May (15%), June (37%), and July (25%).
The most probable danger period in Minnesota, therefore, is late spring and early summer, between 2:00 PM and 9:00 PM. However, tornadoes can and do occur at any time of the day or night.
Despite a higher number of tornadoes reported in recent years, the number of fatalities and injuries due to tornadoes has been decreasing. This is thanks in part to better National Weather Service tools in detecting tornadoes, namely the NEXRAD Doppler radar network installed in the mid-1990s. Also, the ability of alerting the public has improved as well with more National Weather Service radio transmitters and a close relationship with media outlets. An energetic spotter network has also been the key to alerting the public in Minnesota. There have only been 11 deaths due to tornadoes in Minnesota in the last 19 years (1992-2011) and there haven't been multiple deaths due to a single tornado since 1978. In fact, the increasing number of tornadoes reported may be a direct result of improved communications networks, public awareness, warning systems and training.
Most of the deadly and damaging tornadoes occur in groups of outbreaks that often last from 6 to 12 hours. One of the worst such outbreak in Minnesota occurred on June 28, 1979, when 16 tornadoes slashed across the state, from northwest to southeast, in a six and one half hour period. Two additional tornadoes occurred in eastern North Dakota with this system. Many such outbreaks have occurred, including the April 30, 1967 cluster in south central and southeast Minnesota. The largest tornado outbreak in one day in Minnesota is 48 tornadoes on June 17, 2010. The old record was 27 on June 16, 1992 that included an F5 tornado at Chandler.
Just by chance, some counties have not seen a tornado in years. The last tornado reported in Ramsey County was in May 1998. Benton County has gone the longest without seeing a tornado. The last tornado spotted there was on June 16, 1992.
|1950 - 2012||Totals||Annual Average|
|One Year||113 in 2010|
|One Month||71 in June 2010|
|One Day||48 on June 17, 2010|
First tornado reported in Minnesota.
|4/19/1820||11:00 PM (est.)||0||0|
Large factor in the subsequent development of the Mayo Clinic.
|St. Cloud/Sauk Rapids
Deadliest tornado in Minnesota history. 11 members of a wedding party were killed including the groom. The bride eventually remarried.
|Lake Gervias (Ramsey County)
Widely visible throughout St. Paul.
Could have been straight-line winds or microburst.
Second deadliest killer tornado in Minnesota history.
About an hour apart, tornadoes slashed through the cities of Mankato and North Mankato.
Family of tornadoes.
|Western and Northern Twin Cities
Family of tornadoes. Most expensive tornado disaster in Minnesota history (50 million dollars without inflation adjustment).
|South Central Minnesota
Eight tornadoes struck, including three that were rated F4. A four block wide swath was cut in the town of Waseca.
|Gary||7/5/1978||1:56 AM (CST)||4||38|
|Lake Harriet/Har Mar
Tornado tore across the Twin Cities from Edina to Roseville.
|St. Anthony-Apache Plaza||4/26/1984||8:33-8:41 PM||1||52|
Viewed live on TV. See the KARE-11 Newscast part 1 part 2
Last F5 tornado in Minnesota.
Last multiple deaths due to single tornado.
The greatest March tornado outbreak in Minnesota history. Family of 13 tornadoes stuck St. Peter and Comfrey especially hard.
|Granite Falls||7/25/2000||4:57 PM||1||15|
|Wadena and many Minnesota locations
Major tornado outbreak. 48 tornadoes were reported, with three of these tornadoes reaching EF4 (166-200 mph) on the Enhanced Fujita Intensity Scale. Three fatalities were attributed to the tornadoes at widely dispersed locations; Mentor in Polk County, near Almora in Otter Tail County, and near Albert Lea in Freeborn County. A large number of homes in Wadena of Wadena County were damaged or destroyed.