Midwest Overview - August 2011

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Precipitation Variable

Rains varied across the Midwest in August with totals varying from less than 25% of normal to nearly 200% of normal (Figure 1). The highest percentages were in Missouri with other above average totals in central Minnesota into northwest Wisconsin, Michigan and Ohio, and northern Illinois. Totals less than 50% of normal extended from southeast Iowa to west central Kentucky and across southern Minnesota and Wisconsin. Isolated heavy downpours set daily records and led to flash flooding. Midwest drought expanded with increases in the area depicted as Abnormally Dry, Moderate Drought, and Severe Drought during the month (Figure 2).

June-August rainfall also varied across the region but not to the extremes seen in August. Totals varied mostly between 75% and 125% of normal (Figure 3). In many locations, much of the rain came in just a few heavy rains. Monthly rainfall totals varied during the three summer months with few locations consistently wet or dry.
 

Temperatures A Little Warmer Than Normal

After a warm start to the month, temperatures for August averaged slightly warmer than normal (Figure 4). Most areas were a couple degrees above normal with southwest Missouri seeing departures up to 5°F above normal. Hundreds of daily record highs and dozens of record lows were set in August, many in the first week of the month. August readings of 100°F were recorded in Kentucky, Illinois, Iowa, and the vast majority of stations in Missouri.

June-August temperatures were generally a little warmer, averaging near normal in northern Minnesota and eastern Kentucky up to 6°F above normal in southwest Missouri (Figure 5). July was the hottest month of the summer but June and August were mostly above normal as well.
 

Weather Fatalities

More than a dozen people died in August due to the weather. The deadliest incident occurred at the Indiana State Fair on the 13th where a stage collapsed just before a concert. A severe storm with winds estimated in excess of 60 mph knocked down the stage, killing five immediately and two more in the following days and injuring more than 40. Additional deaths occurred in Indiana when a tree fell on a car, two in Wisconsin due to a tornado and a power outage, and three drowned in strong currents on Lake Michigan in two separate incidents.
 

Missouri River Flooding

Flooding continued on the Missouri River in Iowa and Missouri. Summer-long flooding along the river peaked at many locations during August, but continued high water kept fields, roads, and towns inundated. Numerous breaches developed as water-logged levees failed especially in southwest Iowa and northwest Missouri. Miles of I-29 and I-680 remained closed in western Iowa throughout the month and all bridge crossings for more than 100 miles were closed early in the month. Damage to fields and roads was still being revealed at month's end as the water levels slowly decreased.
 

Heat and Drought Take a Toll on Crops

Drought conditions and persistent heat put considerable stress on corn and soybeans in the Midwest. Expected crop yields varied widely but were generally below the 5-year averages and trended lower as the month evolved. Late planting played a role but the timing of the sporadic rains was key to the lower expected yields and high spatial variability.
 

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The Indiana State Climate Office also contributed to this report.
The Iowa Climatology Bureau also contributed to this report.