Assessing Historical Trends in Changing Lengths of Extreme Heat Seasons

Previous research has examined changing growing season lengths and the annual number of days with extreme temperatures. However, limited research exists that explores changes in the first and last occurrence each year of extreme maximum temperatures. Maximum daily temperatures at or above the 95^th climatological percentile have been examined to determine if the “season” of extreme temperature probabilities has been increasing or decreasing across the Midwest and conterminous U. S. Research has found that the changing “heat season” is not uniform everywhere and that there are distinct geographic regions where the “heat season” is decreasing versus increasing. A better understanding of these trends can provide information to the health, recreational, agricultural, and outdoor manual labor sectors. While the number of extreme temperature days may or may not be changing significantly on an annual basis, the timing of those days could play a role in policy, planning, and even educational awareness of the risks of extreme heat exposure. This presentation will highlight the research findings from a climatological perspective of the changing trends in the timing of the first and last occurrence of extreme temperatures throughout a year and provide possible physical explanations along with potential applications and impacts of these findings.