“Corn sweat” blamed for Midwest humidity, is there “sugarcane sweat”?

The Central U.S. was gripped this week by a heat wave that had forecasters warning of dangerously high temperatures and a humidity level boosted by a bizarre atmospheric contributor – corn sweat.

Television meteorologists shoulder-deep in corn broadcast from fields across the nation’s mid-section explaining how 94.1 million acres of ears is making people feel hotter than the mercury actually reads.

Corn sweat, more technically known as evapotranspiration, is the process of moisture from plants evaporating into the air, similar to how humans perspire.

web 072316 pbp CORN SWEAT

And in the nation’s massive agricultural areas, corn sweat can contribute to higher humidity levels, which raised heat index, or feels like temperatures, into the 110 to 115 degree range this week.

“Like a giant wick, a growing corn plant pulls moisture out of the soil,” explained meteorologist and blogger Bob Henson in a post titled Corn and climate: A sweaty topic. “Some of that moisture escapes through the plant’s leaves and enters the atmosphere.”

During a growing season, a leaf will transpire many times more water than its own weight. An acre of corn can give off 3,000 to 4,000 gallons of water each day, according to the U.S. Geological Survey Office.

The hotter the air, the more water it can absorb from leaves, Henson said.

A high pressure system, that is expected to impact the mid-Atlantic states this weekend, made sure temperatures were plenty hot. In central Iowa, temperatures reached near 100 degrees with heat indexes of 114 on Thursday.

So does South Florida with hundreds of thousands of acres of sugarcane and 2 million acres of Everglades suffer from some kind of plant sweat?

Florida Climatologist David Zierden says no.

The corn belt region of the U.S. is much more homogeneous when it comes to large farms than what exists in Florida, and the climate is much drier, “so the contribution from evapotranspiration from the corn fields is a more significant factor.”

“Here in South Florida, especially in the sugarcane region, the natural land cover was wetlands, marsh, and natural vegetation that already had a high evapotranspiration rate, as well as higher ambient humidity to start with,” Zierden explained. “Conversion to sugarcane or other crops just doesn’t make that much of a difference.”


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Sugarcane growing in the Glades near Pahokee, Florida on January 19, 2016. (Allen Eyestone / The Palm Beach Post)

Sugarcane growing in the Glades near Pahokee, Florida on January 19, 2016. (Allen Eyestone / The Palm Beach Post)

Miami-based National Weather Service meteorologist Stephen Konarik agrees, saying the crops over the Midwest U.S. cover more of the land and are more efficient at releasing moisture than sugarcane or the Everglades.

“Here, it’s unlikely that the specific vegetation in the Everglades and/or sugarcane fields would produce enough moisture to have any significant increase in overall moisture content, especially considering we are so near the Atlantic Ocean and the Gulf waters,” he said.

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