What is corn sweat, and is it making the heat worse?
What is corn sweat, and is it making the heat worse?
Every summer when the heat and humidity take over, a “hot” topic emerges: corn sweat! So, what is corn sweat, and is it making the heat worse?
Corn sweat is a fun phrase for a natural process all plants go through called transpiration. Transpiration is when a plant releases water vapor into the atmosphere. It’s a way to cool the plant during hot weather. It’s much like when a human sweats or perspires in an effort to keep cool. As the sweat evaporates in the air, our bodies cool down and return to a safe temperature. And as a corn plant transpires, the leaves release water from open pores. Then, as the water evaporates, the temperature of the plant cools.
Water from the soil also evaporates into the air during hot weather, so the combined release of moisture into the air from both plant and soil is called evapotranspiration.
Corn sweat versus other sources of moisture
Corn sweat is tiny in the grand scheme of our overall weather patterns. Yet millions of acres of cornfields releasing water vapor across the Midwest does have an impact on weather. One acre of corn can produce enough water vapor that would translate to 3,000 or 4,000 gallons (11,400 to 15,000 liters) of water per day!
On average, Iowa grows the most corn across the U.S. Data from the United States Department of Agriculture shows that 13.5 million acres of corn have been planted across the state of Iowa. If one acre (.4 hectare) of corn can produce a minimum of 3,000 gallons of water due to transpiration, that means all the corn across Iowa could, in theory, add at least 40.5 billion gallons (153 billion liters) of water per day into the local atmosphere. This seems like a lot. And it is! But in reality, it’s just a drop in the bucket compared to the other sources of moisture for the United States.
The largest sources of moisture are the Gulf of Mexico and the Atlantic and Pacific Oceans. Approximately 90% of moisture in the air globally comes from oceans, plus rivers and lakes. The remaining percentage comes from plants transpiring.
Corn sweat’s impact on weather
With that being said, corn sweat absolutely can have an impact on local weather! Adding more moisture to the air increases the heat index value. The heat index is how much hotter it feels when the actual air temperature is combined with humidity. High humidity, especially during the hottest days of the year, can have negative impacts on the health of all living beings, especially humans.
When humans are hot, we sweat. As the sweat reaches the surface of our skin, it evaporates in the air, which in turns cools our bodies back to a safer temperature. But when the humidity is high (when there is too much moisture in the air) our sweat can’t evaporate as easily. And this can lead to your body becoming more stressed or overheating.
This means that during the hottest days of the summer, if you live near cornfields, you will feel hotter due to the added moisture in the air. The actual air temperature will not increase due to the moisture, because too much moisture doesn’t allow temperatures to rise rapidly. So while the actual temperature may not reach extreme values, it will feel much hotter.
Also, higher moisture in the air doesn’t allow temperatures to drop quickly overnight, so nighttime and early morning temperatures will be a few degrees warmer due to higher humidity.
Corn sweat and rain
Some people think the excess moisture due to corn sweat can increase rainfall in the area. But it’s important to note that the increase in humidity does not directly create rain. Moisture needs to rise and condense to create clouds. And the water droplets inside clouds need to come together to form larger drops. When these drops get large enough, they then fall out of the cloud as precipitation. While warm, moist air is buoyant and can rise on its own, in order for significant rain or storms to develop, another weather feature (like a cold front or warm front) needs to be present.
Typically a seasonal impact
Corn does most of its growing during the hot summer months. So most corn sweat impacts are felt when it is already hot outside. While the moisture put out by corn and other plants during the summer can make it feel more miserable outside, it is not a year-round impact. Plus, it’s a regional impact. But whether you live in an area surrounded by tall cornfields or a more metropolitan area, take extreme heat seriously, no matter where you call home.
Bottom line: Corn sweat is a process in which corn plants release moisture to keep cool. But it makes people sweat as it increases the humidity in the air, which makes hot days feel even hotter.
Read more: Millions under extreme heat risk across the US
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