The Weird Reason Illinois Is One Of America’s Most Humid States

Here in Illinois, a little-known statute says that you can be ticketed and/or face misdemeanor charges if you don't say "it's not the heat, it's the humidity" at least once per summer. That's what I heard, anyway.

And, looking at the calendar, the months that we say that the most are quickly approaching.

If you’ve ever stepped outside on a late-spring or summer afternoon in Illinois and felt like you just walked into a damp, invisible wall, you’re not imagining things. And no, it’s not just the rain, no matter what Milli Vanilli tried to tell us.

You can actually blame it on the corn.

Illinois consistently ranks among the most humid states in the country, and one weirdly fascinating reason is something meteorologists casually call “corn sweat.” It sounds like something you'd drink at a county fair, but it’s actually a legitimate scientific phenomenon tied directly to how corn grows.

Let's All Learn A Fun New Word That Describes The Corn Sweat Phenomenon

Here’s the deal: corn plants pull water from the soil and release it into the air through their leaves in a process called evapotranspiration. Think of it as the plant version of breathing, except instead of exhaling carbon dioxide, corn releases water vapor.

And not just a little bit of water vapor, either.

A single acre of corn can release 3,000 to 4,000 gallons of water into the atmosphere per day during peak growing season. Now multiply that by the millions of acres of corn planted across Illinois and the Midwest, and suddenly that sticky, heavy air starts to make a lot more sense.

All that extra moisture can boost humidity levels significantly, sometimes by as much as 30 to 40 percent on hot days. Which is why an already hot 90-degree afternoon can feel like you’re living inside a steam room.

So, Just How Humid Is Illinois In Comparison To Other States?

According to a recent breakdown by WorldAtlas.com, Illinois is not alone in our sweaty misery.

States that rival or beat Illinois in humidity include Florida, Louisiana, Mississippi, Hawaii, and Iowa. In other words, we’re keeping company with Gulf Coast steam baths, a tropical paradise, and our corn-growing neighbor to the west.

To be fair, corn isn’t the only culprit. Warm, moisture-rich air flowing up from the Gulf of Mexico still plays a major role in Midwest humidity. But when you combine that with endless rows of corn essentially “breathing out” moisture all day long, you get the full Illinois summer experience: thick, steamy, and just a little bit oppressive.