Ag Weather Forum

The U.S. corn harvest is past the 10% completed mark, with the national completion rate at 11% for the week ended Sunday, Sept. 21, 2025. But even as the focus turns more toward harvest-related topics, the effect of flash drought conditions in the Eastern Corn Belt once again commands attention. The final few weeks of the season have been harsh, as September has mimicked the month of August over this region, with a dry and hot pattern that has drawn large amounts of moisture out of soils. Topsoil moisture now rates 70% or more in the short- to very-short category in Illinois, Indiana and Ohio, according to the USDA weekly crop weather bulletin on Tuesday, Sept. 23.

There's more detail on the significance of this late-season Midwest drought. A look at the USDA Ag in Drought archive illustrates the significance of this late-season Midwest drought expansion. For example, crop years 2016 and 2018 also featured minimal drought conditions during pollination and grain fill, as did 2025. However, those years did not have the onset of dryness that we have seen this year. In 2016, just 2% of U.S. corn areas were assessed in drought as of early September, and that area stayed at 2% by the last Ag in Drought update at the end of the month. In 2018, the early-September Ag in Drought assessment showed 7% of U.S. corn areas in drought and actually declined by one percentage point in the late-September report to 6%.

The weather pattern in this final full week of September offers some moderate to locally heavy rain for the southern and eastern Midwest. Rainfall is certainly beneficial for soil moisture and river transportation improvement. However, with harvest already underway in the region, the rain offers little to no yield benefit; corn yield effects could be considerable. The rain may actually be detrimental to yield due to slowing down or snarling harvest efforts.

It was just one year ago in 2024, when USDA final yield numbers on corn were 4 bushels per acre (bpa) less than the August estimates. The corn yield has already been shaved by 2.1 bpa (186.7 bpa in September versus 188.8 bpa in August). The sharp expansion of corn areas in drought in just two weeks certainly suggests yield will trend lower as we go through the 2025 corn harvest.

Bryce Anderson can be reached at bryce.anderson@dtn.com

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