Iowa corn crop takes a big hit, late in the season.

The major derecho storm that damaged a huge swath of Iowa corn on August 10 clocked winds at 140 mph – a force not seen in the Corn Belt for almost a decade. Although winds greater than 74 mph can occur an average of once a year at almost any point in the Hawkeye State, the last time winds reached 130+ mph was in 2011. Winds of this magnitude do unspeakable damage: during the August 10 storm, 100-foot grain bins were crumpled, apartment buildings were destroyed, and a Cedar Rapids radio tower was thrown to the ground. And millions of acres of Iowa and Illinois corn were decimated.

Iowa corn loss is 185 million bushels.

Using 40 years of sophisticated, weather-based data – as well as modeling comparison data from a similarly destructive derecho – Main Street forecasts Iowa corn loss at 185 million bushels. While traditional models such as satellite imagery and crop progress comparisons forecast many more bushels lost, Main Street Data’s sophisticated techniques consider satellite imagery as well as the crop stage of the lost bushels to calculate its 185 million bushel estimate. Main Street Data specifically ties this estimate of lost bushels to the timing of this recent derecho in mid-August, since storm damage must be precisely calibrated to the crop stage at the time of impact.


Iowa Corn damage after 2020 Derecho

Bushel loss by county, caused by August 10, 2020 derecho storm.

While Iowa corn bears widespread damage, national corn yield forecast still breaks records at 179 bushels/acre.

Main Street Data’s revised corn yield forecast still breaks records, at 179 bushels/acre as compared to the high-range forecast of 183.8 some weeks ago. In addition to the monumental loss to Iowa corn crops due to the derecho, soil moisture is beginning to shorten the maturation process and nip back the production curve — further affecting the national yield forecast. This forecast of 179 Bu/A would break the previous national record corn yield of 176.6 Bu/A in 2017.

It’s critical to note that lost acres – defined as a “total loss” and thus not harvested – are calculated differently in yield forecasts than partially-harvested acres not counted as a total loss. These partially-harvested acres thus bring the average yield down overall, rather than being removed from the equation altogether — and these discrepancies can affect state-specific yield forecasts.

Iowa corn forecast is now 196 bushels/acre, and both Indiana and Minnesota are forecasting record yields.

The record for Iowa corn production is 203 Bu/A, so while many farmers in destroyed areas are tragically suffering full-blown losses, the state overall remains strong at 196 Bu/A. Indiana is yield forecasting at 196 Bu/A as well, and Minnesota is close behind at 195 Bu/A — both record forecasts for these states.

Main Street Data remains committed to keeping everyone informed – both on 2020 corn yields and the 2021 moisture outlook.

With soil moisture still a large factor in final yields, Main Street Data is continuing to monitor Ohio and Indiana in particular for decreased moisture — keeping an eye both on final 2020 yields as well as the 2021 growing season. By forecasting soil moisture six months into the future, continuously throughout the year, Main Street Data forecasts trends that take into account crop stage, moisture depth, and soil aridity duration, to provide the full picture to those who need it — when they need it.


Formed in 2017 and based in Kansas City, Main Street Data brings precise data science practices to the agriculture world by applying sophisticated analytical instruments to massive amounts of field data. Main Street Data’s Progressive WeatherYield tool forecasts crop yields using a proprietary weather-based model.


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