Corn sweat from crops exacerbates humidity during Illinois heat waves

CBS News

4 days ago

Extreme heat is descending on Chicago again this week, and an agricultural phenomenon called corn sweat is making the heat wave this summer even worse.
The U.S. leads the world in corn production, and Illinois grows more corn than any other state besides Iowa. At this time of year, the corn is high, lending its name to the phenomenon of corn sweat.
"But really, all plants do that," said agriculture teacher Joshua Berg. "So, you know, you could just as much say 'soybean sweat.' I guess they haven't got on that marketing yet.
The scientific term for the phenomenon is transpiration. Berg, who holds a master's degree in agricultural education, said transpiration is not like humans' sweat for cooling — it is a vital part of getting water to the plant.
"Transpiration is a process where water is released from the plant's leaves, and that actually helps the plants move water," said Berg.
CBS News Chicago Meteorologist Kylee Miller explained the effects of transpiration are showing up in this week's forecasts.
"Dew points could be about 5 to 10 degrees actually higher, adding with that corn sweat, compared to what Mother Nature is giving us," Miller said.
Other crops, like alfalfa and sugarcane, have higher evapotranspiration averages than corn. The evapotranspiration average for alfalfa is 6 to 8 mm/day for alfalfa and 5 to 7 mm/day for sugarcane, compared with 3.5 to 5mm/day for corn.
Soybeans are in a range comparable to corn, at 4 to 6 mm/day
But it is, in fact, corn's prevalence and growing season that are affecting the humidity now.
"So during the growing season, one acre of corn can release 3,000 to 4,000 gallons of water a day," said Miller. "Here in Illinois, we have about 11 million acres [of corn]."
Those numbers are driving up the forecasts for our summer's second heat wave this week.
The effects of this corn sweat could continue into the weekend. It can result in more rainfall with higher humidity.