Ag Weather Forum

Dry August in the Corn Belt

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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Percent of normal precipitation in the contiguous United States in August 2020 compared to the 1981-2020 average. Extremely dry conditions dominated the West and the western Midwest. (NOAA graphic)

It's no surprise that the United States August climate summary comes in as a very dry month for many areas -- certainly the West, where historic wildfires are forcing many people into refugee status because of their homes getting destroyed -- but also in the Plains and Midwest.

The U.S. National Centers for Environmental Information (NCEI) are cataloguing some big departures above normal on temperatures and below normal on precipitation from August 2020.

Some highlight details in the NCEI report are noted here.

According to the latest climate summary from NOAA's National Centers for Environmental Information, extreme heat in the U.S. Southwest carried August 2020 into the record books as the country's third-warmest August in the 126-year record. At 74.7 degrees Fahrenheit, the August average temperature in the contiguous United States was 2.6 deg F above the twentieth-century average.

Average precipitation in August was in the driest third of the historical record, despite the arrival of two tropical cyclones -- Marco and Laura -- and above-average precipitation across the Mid-Atlantic, the Ohio and Lower Mississippi Valleys, and the Southeast. The dry outcome was driven by below-average precipitation in the Pacific Northwest and well-below-average precipitation across swaths of the Midwest, Southern Plains, the Rockies, and the Southwest.

The dry conditions and high temperatures continued and worsened drought across the West. The percent area of the contiguous United States experiencing some level of drought increased by 7 percentage points in August, leaving nearly 40% of the country in drought.

The parched conditions also led to extreme fire activity in Colorado and California. As of the end of August, three of the fires in Northern California -- the SCU, LNU, and August Complex -- ranked as the state's second-, third-, and fourth-largest on record. Meanwhile, the Pine Gulch Fire in Colorado has become the largest in the state's history."

Let's also make sure that the August dryness effect on crop conditions is noted in this overview. On Aug. 2, Iowa corn crop ratings were 59% good and 14% excellent for a total of 73%. That total declined to 41% good and 4% excellent on Aug. 30 for a total of 45%. And the state's hot and dry calamity peaked in the final full week of the month.

From the Iowa crop and weather summary, as noted by Iowa state climatologist Justin Glisan: "August 24-30 was the driest reporting period of the summer and of the 2020 growing season ... All Iowa stations, with the exception of one, reported below average precipitation ... Much of the reporting period also had temperatures well-above average with the highest departures, on the order of 10-12 degrees, in western Iowa. The statewide average temperature was 77.3 degrees, 6.1 degrees above normal."

Bryce Anderson can be reached at

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