July maximum temperatures in Wisconsin have dropped at a rate of 1.9 degrees per century since 1895, but our friends at NCDC wipe out almost all of this decline by altering the data.

The adjustments are a spectacular hockey stick of cooling the past.

They blame their adjustments on things like time of observation bias (TOBS) but that story doesn’t hold any water.
The next graph shows the peak July temperature recorded at all Wisconsin HCN stations. This is a measurement which can’t be affected by TOBS, because it wouldn’t make any difference if you double counted the peak temperature for the month. It shows that Wisconsin summers were consistently much hotter prior to 1950

And the next graph shows the number of daily July all-time temperature records set or tied at all Wisconsin HCN stations. Once again, this measurement is not likely to be affected significantly by TOBS, and shows that Wisconsin summers used to be much hotter.

The bottom line is that the USHCN temperature adjustments are fraudulent, they hide the decline in US temperatures, and they do them all over the country.
The worst forest fires in US history occurred in Wisconsin during the 19th century. They almost never have large fires any more.

http://www.rootsweb.ancestry.com/~wioconto/PeshtigoFullFireMapOnly.jpg