Agricultural and biological engineering professor Rabin Bhattarai and his colleagues found significant increases in the frequency of daytime extreme heat stress across the Upper Midwest, but some areas sweltered more than others. Urban areas often saw the biggest increases over time, likely as a result of the "heat island" effect, he said.
Photo by Fred Zwicky
CHAMPAIGN, Ill. - Researchers analyzed meteorological data from nine Upper Midwest states from 1979-2021, tracking trends in extreme heat and cold over every 4-kilometer square of that territory. They found striking regional differences in the extremes. Many parts of the Upper Midwest experienced significant upticks in the number of extreme heat days over the 40 years - an increasing trend - while others saw a rise in extreme cold events. Some communities experienced more of both extremes. Others appeared to be more resistant to changes in extreme heat or cold.
The study, reported in the journal Atmosphere, overlaid this data with county-level social vulnerability, said University of Illinois Urbana-Champaign agricultural and biological engineering professor Rabin Bhattarai, who led the research with Illinois graduate student Manas Khan.
"There are many factors that go into the social vulnerability index, the measure that we used," Bhattarai said. "These include income, disability, unemployment, language barriers, housing type and minority status. The idea is that even within a county, even within a city, we see people with very different economic backgrounds, very different living conditions. And if an extreme event occurs, not all people will be affected in the same manner."
The researchers found significant increases in daytime extreme heat stress in parts of Michigan, Wisconsin, Ohio, Indiana and Kentucky from 1979-2021, and on average across the Upper Midwest. Extreme heat stress is the result of temperatures above 90 degrees Fahrenheit for two or more days with high humidity.
