Corn sweat: crop moisture amplifies humidity and heat in US midwest

You won’t believe your ears, but corn is making the extreme heat the US midwest is battling feel more intense, according to experts.

The moisture – or “sweat” – that corn and other crops release in high temperatures is contributing to the humidity in the air in the midwest US, where 55 million people have been under alerts for extreme heat in recent days. The increase in moisture pushes up dew points, making it harder for water vapor to condensate – and for it to feel cooler.

Exacerbating the situation is the fact that the US is the “largest producer, consumer, and exporter of corn in the world”, as well as ethanol, which the country primarily makes from corn kernel starch, according to the US Department of Agriculture . And two states in the grips of the heatwave – Iowa and Illinois – are responsible for a third of US-produced corn.

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That has left residents of those states, along with other prolific corn-producing neighbors, feeling even warmer as they grapple with scorching temperatures forecasted to reach 105F (41C) to 115F (46C).

“It is the plants reacting to that warmer weather. They also then need more moisture, so they’re uptaking more from stored-underground water and bringing that up to the atmosphere that we’re in,” Chris Clark, an agronomist at the University of Wisconsin-Madison told a local CBS news outlet .

One acre of corn, which is a little smaller than the size of an American football field, can can create 3,000 to 4,000 gallons of corn sweat, Clark said.

The climate crisis , caused primarily by the burning of fossil fuels, forest destruction and methane emissions, means heatwaves are increasing “in frequency, duration, intensity and magnitude”, according to the World Health Organization .

A heat dome covered large swathes of the US south-west earlier in August, affecting nearly 23 million Americans and straining energy infrastructure. And in the coming days, a heatwave may soon sweep over mid-Atlantic states, including parts of Pennsylvania, New Jersey, New York, Connecticut and Rhode Island.

Heat is the leading cause of weather-related deaths in the US. According to the US Centers for Disease Control and Prevention, each year about 1,220 people in the US are killed by extreme heat.

The heatwave and the related corn sweat-induced humidity are part of broader extreme weather patterns seen in the US in recent days.

Elsewhere, an Alaska landslide reportedly killed a public works employee who had volunteered to help his community’s government respond to inclement weather during his scheduled time off.

A woman died in a Grand Canyon national park flash flood. Additionally, Hawaii was pounded with rain from Tropical Storm Hone , and California’s Sierra Nevada saw early-season snow .