Doyle Rice

USA TODAY

From muck fires to drunken forests, everyone loves weird science. Here's another one to add to the list: "corn sweat," which is contributing to the fierce heat wave scorching the central U.S.

No, the nation's 94 million acres of corn don't actually sweat, said Mark Licht, an Iowa State University extension agronomist.

Corn sweat is just another way to describe evapotranspiration, the natural process of water evaporating from plants to the air.

Like a giant wick, a growing corn plant pulls moisture out of the soil, according to the National Center for Atmospheric Research (NCAR). Some of that moisture escapes through the plant’s leaves and enters the atmosphere, a process known as transpiration. Water vapor also enters the air from lakes and other surfaces through evaporation. Together, the processes are known as evapotranspiration.

Sweltering heat wave hits USA's three biggest cities

During the growing season, an acre of corn sweats off about 3,000 to 4,000 gallons of water each day, according to the U.S. Geological Survey.

In Iowa, corn pumps out "a staggering 49 to 56 billion gallons of water into the atmosphere each day" throughout the state, the National Weather Service said. That can add 5 to 10 degrees to the dew point, a measure of the humidity in the air, on a hot summer day.

Dew points this week skyrocketed to the upper 70s and even low 80s in parts of the Upper Midwest, which is about as humid as it gets in the USA. Dew points above 70 degrees are considered oppressive.

"We’d be humid, anyway, but we’re more so with the row crops that we have," said Iowa state climatologist Harry Hillaker.

So while the corn sweat isn't causing the temperature to soar, it is adding to the humidity, which makes the outside weather feel even more miserable to people.

"The warmer the air is, the higher the capacity it has to hold moisture," Hillaker said. "That can increase very dramatically as it gets warmer."

Iowa farmers this year planted the fifth-largest corn crop since the 1920s, the U.S. Department of Agriculture estimates. Nationally, it's the third-largest number of corn acres planted since 1944.

Contributing: Donnelle Eller, The Des Moines Register