The Myth of “Corn Sweat” and Heat Waves

Every Midwest summer, especially during humid stretches, you’ll hear it: “The corn is sweating again….that’s why it’s so hot.” It’s a catchy idea, but the science tells a more nuanced story.

What People Call “Corn Sweat”

The term refers to evapotranspiration which is the process where corn plants pull water from the soil and release water vapor through their leaves. At peak growth, a field of corn can move a large amount of moisture back into the atmosphere each day.

The Myth: Corn Causes Heat Waves

While corn does release moisture, it does not create heat waves or drive large-scale weather patterns. Heat waves are caused by atmospheric systems like high-pressure ridges, stagnant air masses, and regional weather dynamics, not crops in the field.

Corn fields can slightly increase local humidity under the right conditions, but that effect is typically small and very localized compared to what people experience during a true heat wave.

What’s Really Going On

When it’s hot and sticky in the Midwest, corn often gets the blame because:

• It’s visible everywhere in summer
• It releases measurable moisture during peak growth
• Humid air already amplifies how heat feels

But that “heavy air” feeling is primarily driven by weather patterns not corn itself.

Expert Perspective

As IL Corn agronomist Megan Dwyer explains:

“Corn is often an easy target when it’s hot and humid, but the reality is that large-scale weather systems (not fields of corn) are what drive heat waves. Corn is simply part of the natural water cycle already happening around us.”

The Bottom Line

Corn doesn’t create heat waves. It participates in the water cycle like every plant does and while it can influence humidity at a very local level, the real drivers of extreme summer heat are much bigger than what’s in the field.