Wisconsin Ranks First in Extreme Heat Which state had the most extreme heat this summer? Wisconsin, according to the organization Climate Central. The group set out to rank the states, with its analysis relying on two main questions: Which state broke or tied the most high-temperature records (after accounting for the number of measurement stations in each state, and the anticipated number of records based on the age of the stations)? Which states had the largest disparities in the ratio between record high and record-low temperatures? Iowa ranked second, and Missouri, third. Readers can glean more details by clicking on various states and categories here.