Hot Asphalt, ‘Corn Sweat’ and Rising Floodwaters: Midwest Swelters Under Intense U.S. Heatwave

June 25, 2025 — A relentless heatwave is scorching large parts of the Midwest, bringing with it dangerous temperatures, flood threats, and even a strange but very real phenomenon known as “corn sweat.”

Cities from Chicago to Des Moines are baking under triple-digit heat, while rural communities are facing both sweltering humidity and rising water levels from recent heavy rains. Forecasters warn that the combination of record heat, moisture-rich crops, and flooded fields is creating a perfect storm of discomfort and danger.

“It’s not just the heat — it’s the intensity and stickiness of it,” said one National Weather Service meteorologist. “We’re seeing some of the worst heat indices in recent years.”

Corn Sweat: The Midwest’s Summer Secret

While asphalt temperatures on roads are reaching up to 140°F, rural areas are getting hit with a unique contributor to the heat: corn sweat. Officially known as evapotranspiration, this process occurs when rows of corn release moisture into the atmosphere through their leaves. It significantly raises humidity levels, making already hot air feel even more oppressive.

“People joke about it, but it’s real,” said a farmer in Iowa. “You stand near a cornfield, and it’s like walking into a sauna.”

Combined with stagnant air and little nighttime relief, the result is dangerous heat indices topping 110°F in some areas.

Flooding Worsens the Crisis

While some towns are cooking under the sun, others are saturated with floodwaters from recent torrential rains that hit parts of Missouri, Illinois, and Indiana. Rivers are spilling over their banks, soaking cropland and threatening infrastructure.

Emergency responders in multiple counties have issued evacuation orders, while others are distributing sandbags and bottled water. The heat has complicated relief efforts, with first responders battling both high temperatures and high water.

“This is a climate double-punch,” said a spokesperson for the Red Cross. “We’re seeing heat and flood impacts at the same time, stretching emergency resources thin.”

Power Grids and Health Concerns

Across the region, energy demand has surged, prompting some power companies to urge customers to conserve electricity. Rolling blackouts have already been reported in parts of Kansas and Nebraska, raising concerns about how long the grid can withstand the stress.

Hospitals are also reporting an uptick in heat-related illnesses, including dehydration, heat exhaustion, and even heatstroke — particularly among seniors, outdoor workers, and children.

Cooling centers have opened across many major cities, though officials warn that transportation to them remains a barrier for rural and lower-income residents.

What Comes Next?

Unfortunately, relief may not come soon. Meteorologists predict that above-average temperatures could last through early July, with little rain expected to cool things down.

The Midwest’s current situation is part of a broader national trend. The southern U.S. is also experiencing extreme heat, while parts of the Northeast are bracing for the same oppressive conditions later this week.

Climate scientists say events like this are becoming more common — and more dangerous.

“This isn’t just summer. It’s a preview of what unchecked climate change looks like,” said Dr. Elena Ruiz, a climate researcher at the University of Michigan.

Stay safe:

• Hydrate frequently
• Avoid prolonged sun exposure
• Check on vulnerable neighbors
• Follow local advisories