Last Friday, October 4th, areas of southeast South Dakota, northeast Nebraska, and northwest Iowa experienced one of the biggest, if not "the" biggest, tornado outbreaks during the month of October. What makes this outbreak so significant is that two EF-4 tornadoes (winds > 165 mph) occurred within a couple of hours of each other. One of the two EF-4 tornadoes hit Wayne, NE, while the other impacted areas around the town of Pierson, IA. In our Nation's history, there has only been five other tornadoes that were EF4 or stronger before October 4th.
To say tornadoes are rare in the month of October across the Tri-State area would be an understatement. Since 1950, only 10 tornadoes have occurred in the Tri-State area during the month of October and none of them were stronger than EF-3 on the Enhanced Fujita Scale. The last October tornado that occurred on October 29, 1996 when a very brief EF-0 Tornado touched down in Sioux Falls at 33rd & Phillips Ave.
When was the last EF-4 tornado in the Tri-State area? Sibley, IA on June 25, 2010. For more information on that event, click here.
When was the last EF-4+ tornado that occurred in the month of October? Before October 4th, 2013, there were only five other tornadoes across the Nation that occurred in the month of October since 1950 that were rated EF-4 or stronger. Those tornadoes occurred in the following states: Nebraska (October 29,1956), Connecticut (October 3, 1979), Oklahoma (October 5, 1970), Louisiana (October 3, 1964), and finally Iowa experienced an EF-5 tornado on October 14, 1966.
The typical peak months for tornado activity in the Tri-State area are May and June. The map below shows where the locations of the tornadoes that previously occurred in the month of October. Map courtesy of NWS Sioux Falls, SD.