Tornado season coming soon: What Minnesotans need to know

Rubble from the greatest March tornado outbreak
Rubble from the greatest March tornado outbreak in Minnesota history includes a grain bin that was tossed two blocks in Comfrey. A family of 13 tornadoes struck St. Peter and Comfrey especially hard on March 29, 1998. One person died and 16 people were injured.
Photo courtesy of the National Weather Service

Severe Weather Awareness Week starts today featuring tornado drills and events that focus on planning for emergencies and building emergency kits.

Tornado season in Minnesota is a long one that runs from early spring well into fall, as warm moisture comes in from the Gulf of Mexico clashing with colder, drier air. The only months during which a tornado has never touched down in Minnesota are December, January and February.

Winter's over: It's Severe Weather Awareness Week
Previously: Storm Ready: Is the Twin Cities prepared?

But when it comes to frequency, June has the most tornadoes, with 37 percent. July ranks second with 25 percent of all Minnesota tornadoes and May is third with 15 percent, according to statistics from the Department of Natural Resources.

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Minnesota's annual tornado count has varied in recent years as Paul Huttner, chief meteorologist for MPR News, pointed out. There were 31 tornadoes reported in 2011 and 37 in 2012, but last year, there were only 15 reported.

"We'll need to see several more years to a decade to see if the decade of the 2000-2010 was a blip or a trend," Huttner said.

In 2010, Huttner wrote that the long-term average for tornadoes in Minnesota since 1950 was 26. From 2000 to 2010 that number had risen to 40 tornadoes per year.

Damage from 1965 tornado
A car sits vertically nestled between trees in Farmstead, two miles from Waconia, in the aftermath of the most expensive tornadoes in Minnesota history on May 6, 1965. A family of tornadoes hit the western and northern Twin Cities, causing $50 million worth of damage, without inflation adjustment from that time. 13 people were killed and 683 people were injured.
Photo courtesy of the National Weather Service

A long view of the state's tornado history shows that from 1950 to 2012, a total of 1,721 tornadoes hit the state, causing 99 deaths and 1,981 injuries, according to the Minnesota Department of Natural Resources.

But as better tools and technology came along for detecting tornadoes in the mid-1990s, the number of fatalities and injuries due to tornadoes has been decreasing, according to the DNR.

Sauk Rapids in 1886
A man and a boy survey the rubble of the deadliest tornado in Minnesota history in Sauk Rapids on April 14, 1886. The tornado hit St. Cloud and Sauk Rapids, and 72 people were killed, and another 213 were injured. The deaths included 11 members of a wedding party, including the groom. The bride eventually remarried.
Photo courtesy of the Minnesota Historical Society

The deadliest tornado in Minnesota history came on April 14, 1886, hitting St. Cloud and Sauk Rapids. It killed 72 people and injured 213. The DNR says that during that tornado, 11 members of a wedding party were killed, including the groom. The bride eventually remarried. The second deadliest took place in Fergus Falls on June 22, 1919, killing 57 and injuring 200.

The most expensive tornado disaster in Minnesota occurred May 6, 1965 when a family of tornadoes struck the western and northern Twin Cities, causing 50 million dollars in damage, without inflation adjustment from that time.

The last incident of multiple deaths from a single tornado took place in Littlefork on August 9, 1993, killing two people but injuring no one.

One memorable tornado contributed to the development of the Mayo Clinic. A tornado in Rochester in August of 1883 killed 37 people and injured 200, according to DNR statistics. The Mayo Clinic website tells that the Sisters of Saint Francis suggested a hospital to care for the sick and injured and Dr. William Mayo and his sons provided the medical care.

By chance, some Minnesota counties have not seen tornadoes in years. The last reported tornado in Ramsey County was in 1998, and Benton County has gone the longest without seeing a tornado -- the last was in 1992, according to the DNR.

Most of the deadly and damaging tornadoes occur in groups, or outbreaks.

The largest tornado outbreak in one day in Minnesota was 48 tornadoes on June 17, 2010, hitting Wadena and many other locations -- Mentor in Polk County, near Almora in Otter Tail County, and near Albert Lea in Freeborn County.

That year, 2010, holds three records when it comes to Minnesota tornadoes. It had the greatest number of tornadoes from 1950 to 2012 -- with a total of 113, according to the National Weather Service.

June of 2010 holds the record as the month with the most tornadoes ever -- 71. And the greatest number of tornadoes in one day also took place in 2010 -- on June 17 with 48 tornadoes.