‘Corn Sweat’ Is Making This Warmth Wave Even Worse
Humid warmth is blanketing the jap U.S. this week, exacerbated by “corn sweat” within the Midwest
The HeatRisk forecast for July 23, 2025.
Nationwide Climate Service/NOAA
Warmth and humidity will as soon as once more smother the jap half of the nation this week, pushing the warmth index to harmful ranges for tens of hundreds of thousands of individuals. Within the Midwest, the humidity might be boosted by a phenomenon known as “corn sweat.”
It’s midsummer, so warmth and humidity are fairly commonplace within the wetter jap half of the nation. It’s unlikely this warmth wave will break information, but it surely might nonetheless be harmful, says Bob Oravec, lead forecaster on the Nationwide Climate Service’s workplace in Faculty Park, Md.
[Read more: Heat Is More Than Just Temperature—Here’s How We Measure It]
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On Monday the warmth and humidity are centered over the Southeast and alongside the Gulf Coast. By midweek, they may transfer northward alongside the Mississippi Valley and up into the Midwest earlier than they shift towards the mid-Atlantic and Northeast across the finish of the week. Highs are anticipated to be round 95 to 100 levels Fahrenheit (35 to 38 levels Celsius) as the warmth wave strikes alongside, however the humidity means it might really feel nearer to 110 levels F (43 levels C) in essentially the most affected areas. Massive swaths of the jap U.S. might be within the “main” HeatRisk class, a NWS classification that comes with warmth, humidity and knowledge on when heat-related hospitalizations are inclined to rise in a given space. Pockets might be within the “excessive” class, the very best on the four-category scale.
A part of the rationale for the oppressive humidity is that “the climate sample has been favorable for moist climate,” Oravec says. “Every little thing is moist, saturated,” which suggests there’s extra evaporation from soil and transpiration from crops. That is significantly true within the Midwest, the place large fields of corn, soybeans and different crops launch moisture because the temperature climbs. The method is akin to how people perspire within the warmth, therefore the nickname “corn sweat.” “The Midwest is known for top dew factors from the vegetation,” Oravec says.
Crops apart, the phenomenon has critical implications for people. Excessive humidity and warmth increase the danger of warmth sickness—it’s tougher for the physique to chill itself through sweating as a result of the air is already so filled with moisture that perspiration doesn’t evaporate. These considerations are particularly excessive for at-risk teams similar to younger kids, older adults, those that have varied well being situations or take sure medicines, individuals who work open air and unhoused individuals.
Extended publicity to such situations can lead to warmth exhaustion, which may trigger fatigue, dizziness, nausea and a cessation of sweating. If an individual with this situation doesn’t get to a cooler location or obtain therapy shortly, warmth exhaustion can progress to warmth stroke, which causes the physique to lose its skill to chill itself, an especially harmful state of affairs. In truth, it may be deadly.
Consultants warning individuals to remain hydrated and keep away from strenuous outside exercise, particularly in the course of the day, when temperatures are highest. There are additionally ideas for holding your house cool. [Read more: Six Ways to Stay Safe Outdoors in Extreme Heat]
These considerations will linger each within the brief and long run. In the long run, warmth waves have gotten hotter and taking place extra continuously than up to now due to the added warmth trapped by greenhouse gases within the environment because of people burning fossil fuels. An evaluation by the nonprofit Local weather Central discovered that human-caused local weather change made this excessive warmth occasion no less than 3 times extra probably for almost 160 million individuals, nearly half of the U.S. inhabitants.
Within the brief time period, climate fashions present humid warmth over the jap U.S. for the following week or two. “The climate sample is simply sort of stagnant and is caught,” Oravec says. “It appears to be like prefer it’s going to be a sizzling few weeks.”