Midwest Heat Wave's Sticky Side Effect: Corn Sweat

Scientists know it as evapotranspiration. Midwesterners may know it by an earthier term: corn sweat. This week's heat wave in America's Corn Belt has put the term into wider circulation, with scientists explaining how the phenomenon can increase humidity—making a 90-degree day feel like 100 degrees or more—and how the effect may be growing more pronounced thanks to warming temperatures.

• Basics: The site AGDaily offers an explainer of evapotranspiration, which begins when plants (not just corn) take in water from the soil through their roots. "Water is transported through plant tissues, where it plays a role in metabolic and physiological processes," and the moisture is then released into the air through the leaves.

• All that corn: As Vox notes, corn doesn't "sweat" more than other plants, but the effect is big in the Midwest because so much corn (thousands of acres) is grown there. "One acre of mature corn can release 3,000 gallons per day," reads a tweet from meteorologist Chris Vickers of WTOL. "This adds to the extreme mugginess we are currently feeling."
• The result: A video explainer at the Weather Channel shows how states such as Wisconsin, Illinois, Iowa, Minnesota, and Nebraska were particularly muggy this week because of the rising "dew point" caused by corn sweat.
• Industrial factor: Evapotranspiration is a healthy attribute of plants, but large-scale industrial plots of land with corn—needed in part to meet ethanol demands, per the AP—change the equation. "Native prairies are diverse ecosystems with a variety of plant species, each with different root depths and water needs, helping to create a balanced moisture cycle," Bruno Basso of Michigan State University tells Vox. "In contrast, corn and soy monocultures are uniform and can draw water from the soil more quickly." The bottom line for Midwesterners is that summers may grow steadily muggier as temperatures continue to rise.

(More corn stories.)