The table below shows the most active tornado years for the entire state of Wisconsin. Wisconsin averages 21 per year.
There were just 16 tornadoes recorded in 2009. Most of last Summer was dominated by cool and dry northwest flow. Wisconsin was often on the cool side of frontal boundaries and north of the jet stream. On the contrary, Wisconsin has seen a large number of tornadoes this Spring and Summer. This Summer has been warmer than normal and much more humid overall. The warmth and moisture are two ingredients important to tornado formation. Fortunately, even with the high number tornadoes, a vast majority of these have been weak and caused little damage. There have been no fatalities this year in Wisconsin from tornadoes.
There have only been four EF2 (Strong) tornadoes to date in Wisconsin and no EF3, EF4 or EF5 tornadoes (Enhanced F Scale).
-Note: The number of recorded tornadoes has been increasing in the past 10 to 20 years. This is largely due to increases in population and more widespread use of cameras. The National Weather Service relies heavily on video and photo evidence, especially when trying to confirm weak tornadoes that may do little damage. There is no doubt that many weak tornadoes went unreported in the 1940s, 50s, 60s and 70s.