Ag Weather Forum

The first day of September marks the start of meteorological fall that extends through Nov. 30. A strong cold front last weekend was a reminder that fall is right around the corner, as low temperatures Aug. 24-25 bottomed out in the mid to upper 30s in North Dakota and northern Minnesota. Mid to upper 40s even showed up as far south as Iowa and northern Illinois on Aug. 25. The temperature outlook for the month of September favors cooler temperatures for a decent portion of the Corn Belt, with a risk for frost by mid-September.

Across the Corn Belt, corn continues to dent. Southern states in the Corn Belt, like Kansas and Kentucky, have over half their corn crop dented according to the USDA's Crop Progress Report released on Aug. 25. Northern states are just getting started, though. Minnesota has 28% of its corn crop dented, while North Dakota is sitting at 16%. Comparing these to the 2020-2024 average, both states are within 2% of average. Corn still has a way to go before it finishes denting.

The amount of soybeans that are dropping leaves in the southern Corn Belt will begin to accelerate. However, cooler temperatures are not necessarily beneficial for soybeans. According to a blog published by the University of Minnesota Extension, soybeans undergo respiration at night that moves starch from leaves into seeds. Respiration slows down when nighttime temperatures dip into the lower 50s, and the crop isn't able to deal with this stored starch. The next day, the soybean plant will struggle to accumulate additional starch. If nighttime temperatures consistently get into the lower 50s, this will limit the seed-fill period and cause the plant to mature. To explore more about weather impacts on corn and soybeans in August and September, the University of Minnesota Extension's blog can be viewed here: https://blog-crop-news.extension.umn.edu/….

Through the rest of this week, below-average temperatures are forecast to continue throughout the Corn Belt. On average, temperatures will span 4-10 degrees Fahrenheit below average through Saturday. Low temperatures could dip into the lower 50s for parts of Minnesota, Wisconsin, and Michigan at times. However, high temperatures will manage to rise into the mid to upper 70s ahead of the cooler nights.

Another trough is expected to build in central Canada and eventually extend into much of the eastern United States by the middle of next week. A cold front will also come through much of the Corn Belt, hitting the western half Sept. 2-3 before pushing into eastern areas Sept. 3-4. While a swath of scattered showers is expected to accompany the front, some of the heaviest rainfall will favor Minnesota and Iowa, with spotty and lighter showers in the Eastern Corn Belt. Another burst of cooler air will follow the cold front as well, with low temperatures dropping into the 40s and 50s late next week for much of the Corn Belt.

Looking ahead through the rest of September, temperatures may moderate somewhat during the second week of the month, but we could be looking at another blast of cooler air from Sept. 11-17 for the central U.S. This round could potentially bring better chances for widespread frost, especially in the northern half of the Corn Belt. A frost in mid-September is not unheard of in northern states and would likely not cause widespread damage like a late August frost would. Given the cooler outlook, fall may be here to stay in the Midwest as producers across the Corn Belt gear up for this season's corn and soybean harvest.

To find more weather conditions and your local forecast from DTN, head over to https://www.dtnpf.com/….

Teresa Wells can be reached at teresa.wells@dtn.com

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