On May 5–8, 1965, a significant tornado outbreak affected much of the Central United States. For four consecutive days, tornado outbreaks produced at least three significant (F2+) tornadoes each day, and at least two violent (F4–F5) tornadoes on three of the four days. The entire sequence generated 37 significant tornadoes, including at least nine violent tornadoes, one of which was rated F5. On May 5, two F4s struck Iowa, including a long-tracked tornado family that injured 11 people. On May 6, an outbreak of six strong tornadoes, four of them violent F4s, affected Minneapolis and St. Paul, Minnesota, and has been nicknamed "The Longest Night", killing 13 people and causing major damages—at the time the most damaging single weather event in Minnesota history. Three of the six tornadoes occurred on the ground simultaneously, and two of them hit the section of Minnesota State Highway 100 (now Interstate 694) and University Avenue in the city of Fridley. Both Fridley tornadoes damaged 1,100 homes and destroyed about 425; total losses reached $14.5 million, $5 million of which was to the Fridley school system.
On May 7, three significant tornadoes hit portions of the Upper Midwest, and beginning early on May 8, a major tornado outbreak affected the Great Plains states, particularly in Nebraska and South Dakota. The outbreak on May 8 produced numerous significant, long-lived tornadoes, including at least three violent tornadoes, two of which were actually long-tracked tornado families. A very large F5 tornado struck Tripp County in South Dakota, and two major F4s tracked across parts of Greeley and Antelope Counties in Nebraska. One of the F4s struck the small village of Primrose, almost totally destroying the settlement, causing probable F5 damage, and killing four people. Additionally, a high-end F3 obliterated a farm in Gregory County, South Dakota, and may have been an F4 as well. Many of the individual tornadoes on May 8 moved north and northwest, an unusual trajectory for supercells in this part of the Great Plains. Many of the long-tracked tornadoes on this date, rather than single tornadoes, were probably tornado families like the two long-lived F4s.
Meteorological synopsis
Temperatures on May 6 were in the upper 70s °F with high dew points, which was considered to be unusual for early May in Minnesota.
|-
|bgcolor=# | <big>F4</big>
|Osage to N of Kendallville
|Floyd, Howard, Winneshiek
|0200
|
|Two large farmhouses were leveled northwest of Kendallville, and about 28 farms were destroyed. All 11 injuries occurred in Mitchell County. The tornado was probably a family of several tornadoes, and it may have been continuous with the F3 tornado near Harmony, Minnesota, listed farther below.
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| colspan="7" style="text-align:center;"|<big>North Dakota</big>
|-
|bgcolor=# | <big>FU</big>
|W of Leal
|Barnes
|2100
|unknown
|Brief touchdown. The tornado was up to wide near Norwood Young America and Waconia.
|-
|bgcolor=# | <big>F4</big>
|SW of Columbia Heights to Fridley to N of Spring Lake Park
|Hennepin, The tornado then became the second of the day to hit Fridley, and even struck the same trailer park in Fridley hit by the previous tornado. Homes were swept from their foundations, and the damage swath was wide. Tree damage in the village was severe. Vehicles were thrown hundreds of yards, and there may have been F5 damage to buildings as well. Cars were carried for , and a truck body was carried and rolled for . Considering this outbreak occurred just three weeks after the Palm Sunday tornado outbreak, quick and successful warnings from the U.S. Weather Bureau and transmission from WCCO Radio kept the death toll relatively low. This was also the first time in Minnesota state history where civil defense sirens were used for severe weather purposes.