What is corn sweat?

Otherwise known as evapotranspiration, corn sweat refers to the process where corn plants absorb water from the soil and release water vapor into the atmosphere through their leaves (Figure 1). Evaporation from the soil surface also contributes to this phenomenon. During peak corn growth, this process can release a large amount of moisture into the air, particularly when soils are wet from recent rains.

The impact on humidity

An acre of corn can release 3,500 to 5,000 gallons of water into the atmosphere every one to two days.¹ This added moisture increases the dew point, which is the best measure of how muggy the air feels. Higher dew points lead to increased humidity, potentially making already hot summer days feel even more uncomfortable and potentially boosting heat index values. In the past, corn sweat has contributed to dew points reaching over 80 °F in the region, a level of mugginess more commonly associated with coastal areas.

Corn sweat and healthy crops

While corn sweat can contribute to uncomfortable conditions for us, it's a sign of healthy and actively growing corn plants. Evapotranspiration is essential for plant growth and is a natural cooling mechanism for the corn crop itself. When plants are stressed, such as during drought conditions, they may reduce this process by rolling their leaves to conserve water, which can limit their growth.

Conclusion

So next time you're feeling the heat and humidity on a hot summer day, remember that the surrounding cornfields may be playing a role. The process of corn sweat, or evapotranspiration, is a natural and important part of agriculture and contributes to the overall moisture in the air during the warmest months of the year. Understanding this phenomenon helps us better appreciate the complex interactions between agriculture and the weather that shapes our environment.

Channel Agronomist
Kelly Siverhus

Sources

¹Wilson, A.B., Lindsey, A., and Ortez, O. 2024. Corn sweat and humidity: A few facts explained. OSU Extension. The Ohio State University. https://extension.osu.edu/about/resources/corn-sweat-and-humidity-few-facts-explained

Friend, D. 2021. How does corn affect Midwest weather? Illinois Extension. University of Illinois Urbana-Champaign. https://extension.illinois.edu/blogs/all-about-weather/2021-07-15-how-does-corn-affect-midwest-weather

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