Summer Temperatures Favored 2017

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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Image by Jim Patrico

Comments about the large size of the U.S. corn crop have eased from the first round of reaction last fall, but there are still questions of “How did that happen?” That’s no surprise; after all, there’s a huge pile of grain now to work through.

A lot of factors contributed to the big harvest in 2017: One was the temperature pattern over the Midwest. USDA research done after the harsh drought and heat year of 2012 definitively showed the impact that midsummer conditions have on crop yield. It showed the month of July is notably important in the crop-season weather fortunes. Information from the Midwest Regional Climate Center bears that out.

In 2017, Midwest temperatures displayed these mid- to late-summer parameters: during July, within 1ºF of normal for the majority of the region; in August, a very cool month saw temperatures average 2.8ºF below normal; and September brought a swing back to above-normal readings as the crop moved into its final segment of the development cycle.

The temperature pattern helped ease the effect of drier conditions that formed during the summer. In early July, the Midwest was almost drought-free, with only 2% of the region identified as being in some phase of drought. However, by the end of July, drought had quadrupled to almost 8% of the Midwest. August saw the total drought area hold almost steady, with 9% of the region in some stage of drought. However, 48% of the region was noted in an “abnormally dry” situation by the end of August. The month’s cooler pattern likely enabled filling crops to take advantage of available moisture.

Conditions were not benign, of course. Severe storms broke out frequently in July, with only five days of the month absent a severe weather report. The August cooler temperatures were below normal by a long way; nearly 500 combined daily low maximum and low minimum temperature records were broken or tied for the month. All this back-and-forth continued what began as a challenging season, with heavy rain during May forcing one of the largest replant efforts on record.

Every growing season has its own character. But, if some overall conditions are met, big production totals are likely to follow. The corn-crop performance in 2017 presents a good example of this truism.

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