St. Peter tornado

A St. Peter resident sorted through the rubble of her home for salvageable items shortly after a tornado hit the community, March 29, 1998. File photo

(This article has been revised to update information about the state's earliest tornado of the year)

Minnesota’s record for the earliest tornado of the year was broken March 6 when one touched down at 5:04 p.m. about a half-mile northwest of Bricelyn.

The EF1 tornado traveled northeast for about 10 miles before dissipating. It damaged trees and campers at Pihls county park at Rice Lake.

The National Weather Service reported the Bricelyn tornado hit more than a half hour before one — previously announced as the record breaker —  touched down at Clarks Grove.

The previous record was set March 18, 1968, when a twister came down north of Truman. No one was injured; however, debris from one farm site was carried a couple of miles to a neighboring property.

The Clarks Grove twister damaged buildings and tore up trees along its path in Freeborn County.

Another March 6 twister, rated F-1 on the Fujita scale with winds up to 107 mph, roared through Zimmerman in Sherburne County.

The latest tornado in any year hit east of Maple Plain Nov. 16, 1931, according to Department of Natural Resources, which compiles the state's weather statistics.

"Our office has data back to the 1880s," said Dan Ruiter, DNR information officer.

Climatologist Pete Boulay said the DNR acts as the historical archive for weather data. Boulay's office works closely with the National Weather Service.

"NWS handles the 'here and now.' They look out the window to the west to see what is coming. Our window faces the east; we look at what has happened."

In Minnesota, tornadoes have occurred in every month from March through November, according to the DNR's website.

The first tornado recorded in Minnesota struck the Fort Snelling area about 11 p.m. April 19, 1820.

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.

Area tornado history

South-central Minnesota has had its share of tornadoes:

• Aug. 17, 1946: Tornadoes slashed through Mankato and North Mankato at 5:40 p.m. Wells was hit about an hour later.

• April 30, 1967: A cluster of eight tornadoes moved through south-central and southeast Minnesota between 6-8 p.m., including three that were rated F4. A four-block wide swath was cut in Waseca.

• March 29, 1998: The greatest March tornado outbreak in Minnesota history began about 4:30 p.m. that Sunday. A family of 13 tornadoes spawned by a supercell thunderstorm struck hard at St. Peter, Comfrey, Hanska and Le Center.

Three of the tornadoes during the disastrous weather event resulted in more than $235 million in damage. Two people were killed and more than 20 were injured.

Seven counties in southern Minnesota were later declared federal disaster areas.

Gustavus Adolphus College's campus in St. Peter lost more than 2,000 trees and almost 80 percent of its buildings' windows were broken. (The students were gone because of spring break.) Three-thirds of Comfrey's structures were either damaged or destroyed, including the community's school.

• Aug. 24, 2006: A tornado, rated FO hit the ground north of Searles in Brown County shortly after 5 p.m. and tore across corn and bean fields until it stopped about three miles northeast of New Ulm. Two people were injured when semis traveling on Highway 15 were blown off the road.

A second tornado, rated F3, started around 5:30 p.m. and was on the ground for 33 miles in Nicollet and Le Sueur counties. It's path was tracked from west-southwest of Nicollet, through the town of Nicollet, to the southern edge of St. Peter, across northern part of Kasota, to Lake Emily, then northwest of Waterville. The tornado killed one person and injured 37.

Tornado activity

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 percent), June (37 percent) and July (25 percent).

Tornado activity during December, January and February is concentrated in the southeastern states and along the Gulf Coast. As spring progresses, tornado occurrence moves north and west across the central Mississippi and Ohio river valleys. By summer, the potential threat of tornadoes has spread across the continental United States and southern Canada.

Activity gradually retreats in the autumn months 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 that 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 Tornado Alley, the part of the central United States with the maximum annual occurrences in the country.

Tornadoes can and do occur at any time of the day or night. Late afternoons through mid-evenings during late spring and early summer is the time frame that's the probable danger period for Minnesotans.

Most of the deadly and damaging tornadoes occur in groups of outbreaks that often last from six to 12 hours. One of the worst such outbreaks in Minnesota occurred on June 28, 1979, when 16 tornadoes slashed across the state, from northwest to southeast. Two additional tornadoes occurred the same day in eastern North Dakota with this system.

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 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 embedded in trees and boards after a tornado.

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