Midwest Heat Wave Threatens Crops as Corn Sweat Intensifies Conditions
Heat index spikes and storm activity put stress on agriculture across the Corn Belt
High temperatures and surging humidity are putting Midwest agriculture under intense stress, as meteorologists warn of a prolonged period of excessive heat and scattered storms. At the center of it all is "corn sweat"-moisture released by corn crops during peak growth that's now adding a new dimension to weather challenges in late July.
"Heat index temperatures are the real issue with this extra humidity," said Jeff Andresen, Michigan State climatologist, during a recent USDA Midwest Climate Hub Outlook webinar.
NOAA CPC graphics highlight areas at risk for extreme heat and significant rainfall from July 24 to 30, 2025.
Dennis Todey, USDA Midwest Climate Hub director, emphasized that the corn crop is actively transpiring large amounts of moisture in response to the heat, compounding already high dew points across the region.
"We're heading into the hottest stretch of the year, and it's going to run above normal," Andresen added.
Hazards on the Horizon
The Climate Prediction Center (CPC) warns of two key hazards through the end of July:
Dangerous heat across much of the Midwest
Heavy rainfall potential, especially in northern areas
Historically, the last two weeks of July into early August represent the climatological peak of summer. This year, the combination of heat and persistent atmospheric moisture is pushing heat index values to extreme levels, amplifying risks for crops, livestock, and ag laborers.
Temperature and Precipitation Outlook
Forecast maps for July 28 to August 1 show continued above-normal temperatures from the central Plains to the eastern U.S. Corn and soybean fields in good condition are adding to ambient humidity, potentially increasing heat stress across operations.
Map of the U.S. displaying projected temperature trends for July 28 through August 1, 2025.
At the same time, an active jet stream and storm track across the Upper Midwest is expected to continue, delivering 2+ inches of rainfall in central areas, while drier conditions persist in the northern and western parts of the region.
The 6-10 and 8-14 day outlooks confirm that warmth will dominate late July, especially in central and eastern zones, while precipitation forecasts remain mixed. Areas in the northern Great Plains may stay dry, while parts of the eastern Corn Belt could see wetter-than-normal conditions.
U.S. weather map illustrating the 6-10 day precipitation forecast.
August Outlook: Modest Relief or More Pressure?
Looking ahead into August, NOAA seasonal outlooks suggest:
Mild warmth over the northern Midwest
Stronger heat anomalies in coastal regions
Drier-than-average outlooks for the Great Plains
Improved moisture in parts of Illinois, Indiana, and Michigan
These patterns could help ease drought in the eastern Corn Belt, but may fall short for growers in the western regions.
NOAA seasonal maps depicting nationwide forecasts for temperature and precipitation.
Ag Implications: Risk Management Now Critical
This prolonged stretch of hot, humid conditions coinciding with peak crop development raises multiple concerns:
Increased heat stress for field workers and livestock
Reduced efficiency in irrigation and cooling systems
Greater pressure from fungal diseases
Delays or complications in input applications due to wet fields
Farmers are encouraged to monitor heat index forecasts, manage irrigation wisely, and stay connected to USDA and NOAA climate updates to make timely agronomic decisions.
