3.5 is generally the kind of GPA threshold that becomes stressful and risky for students who need it for some purpose (pre-med, scholarship renewal, get into a major). http://www.gradeinflation.com/Wisconsinmadison.html says that Wisconsin’s overall average GPA was 3.20 in 2007. Wisconsin discloses grade distributions for its courses at https://registrar.wisc.edu/course_grade_distributions.htm .
Note that most of the engineering majors at Wisconsin have lower GPA thresholds than 3.5 core / 3.0 overall to gain admission to the major.
Note also that Wisconsin’s grading system does not use +/-, but has half-step grades. For example, between A and B grades, there is an AB grade that is 3.5, rather than A- = 3.7 and B+ = 3.3 grades.