Midwest Overview - July 2010

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Heavy Rains Were the Big Story in July

Precipitation for the month varied from less than 25% of normal to more than 300% of normal (Figure 1). Where it rained, it poured. Heavy rains fell throughout the month and across the region with totals over 10" surprisingly common (Figure 2). Large areas from Iowa and central Missouri to central Wisconsin received 4" or more above normal (Figure 3). Flash flooding occurred on many days. Rivers flooded, particularly in Iowa, Wisconsin, Illinois, and Missouri (Figure 4). There were more than 1100 daily precipitation records set in July with over 200 in each of Missouri, Iowa, and Wisconsin (Figure 5). Monthly precipitation records were also set at 46 Cooperative Stations including 26 in Wisconsin. Thirty-eight Midwest stations recorded their 2nd wettest July and another 40 recorded their 3rd wettest. Oelwein, Iowa (Fayette County) recorded 20.33" for the month, shattering its all-time record of 13.30" from June 1925.
 

Temperatures Slightly Above Normal

Midwest temperatures ranged from near normal in the west to about 4°F above normal in the east (Figure 6). Minimum temperatures (Figure 7) were more above normal than maximum temperatures (Figure 8). The vast majority of the daily temperature records in July, 485 out of 575, were record high minimum temperatures.
 

Dam Failure Drains Lake Delhi

Nearly 1000 lakeside properties lost their lake when an earthen dam failed in Delaware County, Iowa. Heavy downpours fell on the 22nd and 23rd fell across northeast Iowa into northwest Illinois with totals over 10", and in some locations even topping 12". The Maquoketa River, which feeds Lake Delhi, rose to more than 10 feet above flood stage, 3 feet above its previous record, and overtopped the earthen dam built in the 1920s. The dam began to erode and the breach continued to grow as the lake emptied in about a day. Downstream flooding caused evacuations of two towns but no deaths or injuries.
 

Flash Flood Fatalities

Numerous flash flood events occurred across the Midwest in July. Three of the events were blamed for four fatalities. On the 17th in Pike County, Kentucky, two people were killed. On the 20th in Hannibal, Missouri (Pike County), one death was blamed on the flooding. The third event was in Carter County, Kentucky on the 21st with one fatality.
 

Lightning Fatalities

Two lightning fatalities were reported in the Midwest in July. Near Ft. Knox, Kentucky (Hardin County) on the 27th, a young woman was struck and killed. The following day a man was struck and killed while biking in Pontiac, Illinois (Livingston County). At least three others were struck in the Midwest during the month, two in Milwaukee, Wisconsin (Milwaukee County) on the 22nd and one in Duluth, Minnesota (St. Louis County) on the 27th.
 

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