Here is a plot of the tornadoes which occurred in Wisconsin in 2013:
It was a relatively quiet year with only 16 tornadoes.
More specifics on the 2013 Wisconsin tornadoes are available from this pdf document.
Wisconsin averages 23 tornadoes per year.
Below is the average number of tornadoes per month.
|Average 1981-2010 (Official)|
NWS - Milwaukee/Sullivan