Here's how corn fields contribute to thunderstorms in the Midwest

AccuWeather

Just one acre of corn can put as much as 4,000 gallons of water in the lower atmosphere, so how does that affect the weather? AccuWeather's Matt Benz breaks it down.

Transcript

00:00As summer continues, millions of corn plants are pumping moisture in the air,

00:04cracking up the humidity in a big way.

00:06So to help explain this whole concept of corn sweat,

00:09we're now joined by AccuWeather Midwest expert, meteorologist Matt Benz.

00:13Mr. Benz, you spent a lot of time working in the Midwest, the Upper Midwest.

00:16I know this is an area where you're from.

00:18Corn sweat's a big driver in the moisture content here.

00:23Yeah, it certainly is.

00:23And the technical term of apotranspiration,

00:26where you are basically taking water from the corn and putting it into the atmosphere.

00:31And a corn field, a typical corn field, an acre of corn can put as much as 4,000 gallons of water

00:38into the lower atmosphere.

00:40So we talk about the corn belt, the corn sweats.

00:42This is a general area that we're talking about from the Upper Midwest

00:45through the northern portions of the Ohio Valley.

00:47This is generally an area that you end up seeing more enhanced moisture,

00:50that low-level moisture, this time of the year,

00:52typically from mid-July into the first week of August,

00:55as that corn is peaking,

00:57that's when you get the peak amount of moisture that is being put into the lower atmosphere.

01:00So that is a concern.

01:01If you're walking outdoors, you can certainly feel it,

01:04but it also can contribute to moisture in the lower atmosphere.

01:07That can be, well, rain as well,

01:09which can fuel heavy thunderstorms for the area.

01:12And we've seen a lot of that over the past five days.

01:14We've been dealing with some drenching downpours.

01:17And there you can see the footprint of the corn belt

01:18superimposed with this five-day radar-estimated rainfall map.

01:23And we've got more coming, too.

01:25Yeah, more rain is coming.

01:26Now, when we look at this map, it's not all directly coming from the corn.

01:30Of course, there's other moisture sources out there, such as the Gulf of Mexico,

01:33another one that I'll get to in just a moment.

01:35But it certainly does have a bit of an impact as far as what it feels like outside.

01:38And, of course, contributing to at least some enhanced moisture.

01:42Now, dew points today, that's a measure of moisture in the atmosphere

01:44lower than what they were yesterday.

01:46We saw many locations across Iowa, southern Minnesota,

01:49eastern Nebraska that were in the 80s yesterday for dew points.

01:52And to give you an idea, why is that a big deal?

01:54Well, that was one of the most humid places in the lower 48 states,

01:58including the Gulf Coast of America and as well as much of the east coast of Florida.

02:04So it's not just that we're talking about a sweaty day.

02:08It's some of the most humid air mass that we see across the region.

02:11Of course, when you look at the values here,

02:13once you start getting into those 70-degree dew points or higher,

02:16that's exceptionally humid, some would even say oppressive out there,

02:19especially when you start crossing that node around 80 degrees or higher.

02:23And like I mentioned earlier,

02:24it's just not the corn that's necessarily contributing to the value here.

02:28We have a big area of high pressure across the southeastern U.S.

02:31and around the periphery of this, what we call monsoonal flow,

02:34pulling moisture up from the subtropical regions of the earth.

02:38So not only is this moisture from the corn down here that serves the earth,

02:41but if you go up 5,000 feet, you also have a lot of moisture there as well.

02:45And that addition of both those moisture sources can really help drive those dew points higher here across the region, Jeff.

02:53And Matt, obviously the corn is not going anywhere,

02:56but there will be a bit of what we might call an air mass exchange.

03:00There's going to be a shift in the wind coming up later this week.

03:03How will that impact the quality of life there in the upper Midwest and even in parts of the plains?

03:08Yeah, it will improve quality there, Jeff.

03:11It will help to knock those dew points down,

03:13possibly into the 40s and 50s here as we head into this weekend and early next week.

03:17And really, once you get into early August, that impact from corn starts to go down.

03:21Once it stops growing, it stops contributing so much moisture to the lower atmosphere.

03:24So in general, you do see an improvement generally in the month of August

03:28with regards to humidity across the upper Midwest and for this region.

03:31And it looks like Mother Nature is going to help out as well

03:34with the cold front coming through here later on this week.

03:36It's really good to see those yellows return to the map there with flow from the north

03:40come Wednesday and Thursday.

03:42Still the steamy in Iowa at that point on the map,

03:44but even into Thursday, we'll get a bit of a break.

03:46Meteorologist Matt Benz, thanks so much for breaking down the details.

03:49As always, Matt, you're great.

03:50And thank you.

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