Formula For A Productive Summer

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
Connect with Bryce:
Image by Pamela Smith

The U.S. corn crop had a wide variety of weather to deal with in the 2018 season. But, by the time everything was over, large yield and large total production are likely to be keyed into the spreadsheets. After all the yield monitor data is downloaded, corn yields will be either close to or at a new record.

In addition to the big yields, we saw crop maturity move on an early track, resulting in harvest beginning a week or two earlier than average. These two features seem to be opposites; but, the timing of weather patterns ties them together.

Let’s look at yields first. After a warm to hot late May and June following planting, central-U.S. temperatures in July were mild and favorable for corn pollination. Temperatures in the Great Plains were 2ºF or more below normal. Temperatures in the Midwest and Southeast were also cooler than normal for almost the entire month.

RECORD EARS. This was key to high-percentage pollination. As a result, USDA noted the highest number of ears on record in its combined 10 objective yield states of Illinois, Indiana, Iowa, Kansas, Minnesota, Missouri, Nebraska, Ohio, South Dakota and Wisconsin.

Now, add August temperatures to that scenario. For the majority of the primary U.S. grain-producing states, August temperatures were either normal to slightly above normal or below to even much-below normal. This temperature pattern allowed some heft to be put into the grain. That means fewer kernels will be needed to fill a bushel of corn; and, thus, more bushels and higher yield. In one Midwest late-summer yield estimate, the difference in kernel depth and development amounted to more than 10% heavier kernels compared with last year. I’m no grain-weight expert, but a double-digit percent increase sounds noteworthy to me.

HEALTHY WEATHER. The reason crop maturity was early can be attributed to two features: first, the very warm to hot late-May and June temperature pattern led to some robust growing degree day (GDD) numbers in the first half of the season. Those hearty GDD totals early on led to notable advances in crop vegetative growth and, thus, an earlier onset of pollination.

ABOVE NORMAL. Meanwhile, July and August, overnight temperatures were mild and above normal, resulting in continued large GDD numbers, even with daytime temperatures generally not reaching stressfully hot categories. (Growing degree day calculation ceases when temperatures exceed the mid-80sºF.) In some areas of the central U.S., GDD totals between mid-April and August were 20% above the average during the past 11 years.

In general, the 2018 U.S. corn crop weather pattern had a sequence of acceleration and then cruising. That’s a formula for some big promises for the total crop this year.

Read Bryce’s weather blog at



Past Issues