Impact of June Rain on Iowa Corn Yield

One Minute Summary

  • News stories have recently reported negative impacts from excessive rainfall in northwest Iowa
  • June 2018 will be Iowa’s 7th wettest June in the last 40 years
  • CropProphet quantification of the impact of June rainfall in northwest Iowa reveals yield losses of up to -16 bushels/acre locally.  But this has relatively little impact on the U.S. national corn yield forecast.
  • Don’t get caught up in locally significant weather hype.  CropProphet quantifies the impact of weather on crop production and yield.

Quantify the Impact of Weather on Corn Yields

CropProphet is designed to quantify the impact of weather on U.S. corn, soybean, and winter wheat crop yield and production.  The product enables analysis of the impact of weather on local, state, and national crop production and yields.  In this post we take a look at a specific event that occurred during June 2018 to demonstrate the benefit and discuss its implications.

We have seen reports of the negative impact that recent rains are having on fields in northwest Iowa, but as is typical of virtually all discussions of weather’s impact on crops, the analysis is rather generalized and leaves it up to the reader to determine the actual impact on final yield and production.

A Wet June 2018 in Iowa

June 2018 will go into the books as a wet month for much of Iowa.  As of June 26th, we estimate that the month will rank as the 7th wettest June across the state in the last 40 years.  The map below shows county level precipitation estimates for Iowa, assuming that normal rainfall occurs in the last few days of the month.  Many counties have seen greater than 6 inches of rain so far this month and quite a few have experienced greater than 8 inches of rain.

A further analysis of June rainfall compared to normal totals is below.  Many counties have seen over 150% of their normal rain for June, and the three northwesternmost counties have experienced more than twice their normal rainfall.   It goes without saying that some rain is good for crops; but too much rain can be very bad for corn, especially early in the season.

Impact on Iowa Corn Yield

What is the impact of the recent heavy rain on corn yield?   CropProphet can answer this question.  The product is designed to enable the quantification of weather impacts.  Numerous weather parameters can impact yield, but we can extract the yield impacts of single variables in specific regions of the country.  The effect of this month’s rain on estimated final yields is shown in the map below: there are localized impacts of -8 to -16 bushels/acre.  While this seems like a dramatic impact, the months of July and August have yet to occur, and the weather during these months may mitigate or eliminate the negative impact of the recent heavy rains.

June Rain Impacts on Corn Yield - Iowa

One of the benefits of using an objective crop production forecasting system is that it can help to cut through market hype that may cause irrational market moves.  Indeed, these irrational market moves become valuable trading opportunities when using a reliable crop yield forecasting system.  It is important to ensure that the impact of any single weather event is understood in the context of the impact that weather is having on the overall crop across the country.  After all, there are approximately 1600 counties in the U.S. that grow corn.   Weather can certainly have dramatic and widespread effects in many of those counties, as it did in 2012, but a localized weather anomaly will generally have only a small impact on the overall national yield or production.

A wider look at the same quantification of June precipitation impacts for the United States is shown below.  It has certainly been a difficult June in northwest Iowa and southern Minnesota, but the net effect of precipitation across the US has been nearly neutral; our quantified impact of June precipitation on U.S. national corn yield is -1.3 bushels/acre.  A few other areas show significant impacts, but the dominant signal is clearly in northwest Iowa and southern Minnesota.

The analysis shown here illustrates how CropProphet quantifies the impact that weather has on crops.   By combining a wide variety of predictors, we provide an objective quantification of the impact of weather on crop yields and production.   Subjective market commentary can help provide context, but too often it leaves the reader to estimate the true impact of the weather on crops.   CropProphet ensures you no longer have to guess.

Avoid the Hype. Get the facts.  Use CropProphet for your grains markets intelligence.