Study Shows Dangerous Heat Becoming More Frequent In Midwest

By Samantha Abernethy in News on Jul 25, 2012 10:10PM

A study of weather patterns shows dangerously hot weather is becoming increasingly common in the Midwest, and the variability of weather in the Midwest makes the region particularly susceptible to heat-related illness.

Earlier today WBEZ spoke with researchers from The Union of Concerned Scientists, a nonprofit science organization that studies global warming trends. Researchers put together "Heat in the Heartland: 60 Years of Warming in the Midwest" by analyzing weather data from the last six decades. It did not include data from our current scorching summer.

Our lack of practice with heat is what makes it particularly dangerous, though. One of the researchers told WBEZ that while Florida is consistently warmer, no one dies from the heat because it's the same every day.

The study focuses on dangerous weather situations, taking high temperature, lack of cooling relief at night, and high humidity into consideration, as they all contribute to heat-related illness. The study shows these types of "air masses" have become more common in the last 63 years, and the city now has, on average, four more days per summer of the most intensely hot weather.

That's coming with less relief, too. We now see, on average, seven fewer cool days per summer. See the full report on Chicago's weather.

Nighttime cooling is critical for reducing heat stress from higher daytime temperatures. However, nighttime temperatures for the two most dangerous types of summer air masses have risen over the past six decades. Temperatures on hot, humid nights have increased by 1.7°F each summer, on average, while temperatures on hot, dry nights have risen by 2.6°F. In Peoria, overnight temperatures have increased on very hot and humid, hot and dry, and cool and dry nights.

Chicago now also has one extra heat wave—three or more consecutive days with dangerously hot air masses—each summer, on average. A 2009 study projected that the city could face an average of 30 days with temperatures of 100°F or above each year by the end of this century under a scenario with higher global warming emissions. The number of such days would rise by only eight each year under a lower-emissions scenario.