STORY CITY, Iowa A fierce windstorm on Monday, Aug. 10, leveled a massive chunk of farmland in the top U.S. corn growing state.

According to data from the United States Department of Agriculture, nearly 20% of all U.S. corn is grown in Iowa, and the state produced over 2.5 billion bushels of corn last year.

The dangerous storm classified as a derecho ripped through South Dakota and Nebraska before it reached the cornfields in Iowa. The storm continued on to hit parts of Indiana, Illinois and Ohio.

According to the National Weather Service, winds as high as 100 mph were recorded during the storm, causing damage to homes, buildings and farms, while leaving tens of thousands of people without power.

The word derecho derives from the Spanish word for straight, and according to the definition given by the NWS, a derecho is a long-lived wind storm that travels over 250 miles. It also has to have winds that exceed 57 mph at most points along the storm path.

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Angie Rieck-Hinz, field agronomist with Iowa State University Extension, said the derecho on Aug. 10 was estimated to stretch 770 miles.

Rieck-Hinz monitors crop production in nine counties in north central Iowa. She said the storm seemed to pick up intensity as it moved across Iowa.

Some of the worst hit regions in Iowa were in Greene County, Boone County, Story County and counties east from there, said Rieck-Hinz.

"Anything from about (U.S.) Highway 20 to Interstate 80 was probably impacted severely," she said.

Many of the regions that were smacked on Monday by the storm were previously facing drought conditions.

"You can see a good chunk of Iowa showing up as abnormally dry before the storm," said Rieck-Hinz looking at a drought monitor map from Aug. 4. "Then as we move westward we get into moderate drought, severe and extreme drought."

Hurricane-force winds

The top windspeed that was clocked in Iowa was 131 mph, said Rieck-Hinz.

"That's hurricane-force winds," she said. "There's a lot of flattened buildings, flattened farms, lots of trees down and still a good chunk of Iowa that doesn't have any power yet."

Rieck-Hinz said it took more than 24 hours for her power to come back in northern Story County where she lives. The crop damage she's seen in her area is "totally flattened and leaning corn," she said, adding that there is also some hail damage.

"But it gets progressively worse as you go east," she said.

In Marshall County, which neighbors Story County, Rieck-Hinz said there's "tens of thousands of acres of flattened corn".

She said that derechos are not uncommon for Iowa to experience in summer, but the storm on Aug. 10 was different than previous ones.

"Nothing we've seen with this much widespread damage, across the central to eastern third of the state," she said.

She said the scope of the crop damage is still unknown. On Tuesday, Aug. 11, Iowa Agriculture Secretary Mike Naig said that the storm impacted potentially 10 million acres of farmland and millions of bushels of grain storage.

Rieck-Hinz said there's been numerous reports of lost livestock buildings, but no reports of injured or dead animals.

"But that doesn't mean that hasn't happened," she said. "I've seen pictures of pig barns with the building entirely gone, and just pigs standing on concrete floors."

First steps to recovery

Rieck-Hinz said she's not hearing from a lot of farmers right now and doesn't expect to for a little while yet.

"We still have a lot of people without power, and they're attending to their own personal and livestock needs," she said. "People are still taking care of the damage cleanup even though we're two days later."

She said Extension hasn't been out in the fields to examine crops yet either, because a lot of roads are still closed and power lines down.

"We just don't have enough boots on the ground to get out and assess all these damages," she said.

Most farmers will understand what their crop insurance will cover of the storm damage, Rieck-Hinz said. Extension will eventually ask farmers to assess how much of the crop is root-lodged and how much of the crop damage is green snap.

If the crop damage is green snap, she said it's a one-to-one yield loss, meaning the loss in yield is proportional to the number of affected plants.

"So if 100% of your field is snapped, that's 100% yield loss," she said. "It's pretty severe."

But before looking at crop insurances, Rieck-Hinz said that Extension staff is focused on immediate safety at farms. Priorities are power safety and getting power back to farms, along with food safety and having enough supplies to make it through the aftermath.

"Right now, we're doing the immediate response stuff and focusing on safety issues, then we'll move on to more crop response," said Rieck-Hinz.