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Chicago heat: How “corn sweat” could push the heat index close to 110°F

From La Nación · () Spanish

Translated from Spanish and summarized by DistantNews. Read the original for the full story.

At a glance

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  • The National Weather Service forecast temperatures near 90°F in parts of northern Illinois as late-season heat and humidity affected the Chicago area.
  • Corn evapotranspiration can add moisture to the air, allowing a 90°F temperature to produce a heat index near 105°F and, in some areas, 110°F.
  • Health risks rise with the combination of heat and humidity, particularly for older people, children and those spending long periods outdoors.

A late-season heat wave in the Chicago area could feel close to 110°F because moisture released by Illinois cornfields may add to already high humidity.

The National Weather Service forecast temperatures near 90°F in parts of northern Illinois. Ashish Sharma, climate and urban sustainability lead at the University of Illinois Urbana-Champaign’s Discovery Partners Institute, called the event unusual and potentially dangerous for the end of the season. Normal high temperatures in Chicago during this period are about 80°F.

“Corn sweat” describes crop evapotranspiration. Corn plants draw water from the soil and release vapor into the atmosphere through small pores in their leaves. When the air already contains substantial moisture, sweat evaporates less efficiently, reducing the body’s main cooling mechanism. Sharma said air temperatures around 90°F could therefore produce a heat index near 105°F, and in some places near 110°F.

This heat wave is unusual and a significant and potentially dangerous event for late in the season.

· Ashish SharmaThe University of Illinois Urbana-Champaign climate expert described the late-season heat affecting Chicago.

Illinois lies within the Corn Belt and has about 11 million acres of corn planted each year. During peak growth, one acre can release between 3,000 and 5,000 gallons of water per day. Across the state, mature crops can transfer more than 35 billion gallons of water into the atmosphere daily. Evapotranspiration usually peaks from mid-July through late August, but its effect on humidity can continue during heat episodes in early September.

September heat is not unprecedented in Chicago. A 2015 National Weather Service analysis found that since 1980, September has averaged about three days with highs of at least 90°F, although that does not happen every year. The combination of heat and humidity remains the main health concern, especially for older people, children and those outdoors for extended periods.

When the air contains a lot of moisture, sweat cannot evaporate as effectively, and evaporation is the body's main cooling mechanism.

· Ashish SharmaSharma explained why corn-related humidity can make temperatures feel substantially hotter.
About this summary

Originally published by La Nación in Spanish. Translated, summarized, and contextualized automatically by DistantNews, with a note on how the source frames the story. Not individually reviewed before publishing. How this works.

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