For 2014, officially 20 tornadoes have been observed affecting a part of Wisconsin. Seventeen of the 20 tornadoes that have occurred this year were during June. The strongest tornado rated EF3 occurred on June 17th shortly after midnight (CDT) and severely damaged the Country View Elementary school in Verona. At least 30 homes sustained major damage from this tornado. The tornado was only on the ground for several minutes and had a path length of about 1 mile. Tornadoes ranked EF3 have estimated wind gust speeds of 136 to 165 mph.
Wisconsin averages 23 tornadoes per year, with most of the tornadoes occurring in the 3 to 9 pm period. The peak hour for tornadoes is 6 to 7 P.M.
The peak tornado season in Wisconsin is May through August, with June having the greatest number of tornadoes. A record-setting 62 tornadoes occurred in 2005, followed by 46 in 2010. In 2008, Wisconsin had 38 tornadoes, including one EF3 tornado in western Kenosha County on January 7th. The "average" Wisconsin tornado has a 7 to 8 minute duration, a path length of about 4 to 5 miles, and a damage width of about 120 yards.
Here is a document which lists the tornadoes that have been observed in Wisconsin so far this year. Through June the list is complete. After June, the list remains preliminary and entries may be changed as more details become known about the tornado.
The below graphic illustrates the 2014 tornado tracks across Wisconsin that are listed in the above document.
Since most of the tornadoes this year occurred in south central Wisconsin, here is a close up of this area. Click on the image for a larger view.
National Weather Service - Milwaukee/Sullivan