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August 15-21, 2023

  • Weekly Summary

August 15-21: Michigan Rains, Minnesotan drought, and Cool Throughout

Temperatures Fall Largely Below Normal

There were almost no areas of the Midwest with above-normal temperatures this past week. In fact, quite a large part of the region saw temperatures averaging below normal. The entire states of Indiana, Kentucky and Ohio fell 2°F to 4°F below normal (Figure 1). Indiana, Ohio and Kentucky saw temperatures average 2.7°F, 1.7°F, and 2.2°F below normal. Minimum temperatures were anywhere from 2°F to 5°F below normal in every Midwest state except Minnesota and Wisconsin, which averaged closer to normal (Figure 2). Maximum temperatures did in fact come in above normal from Iowa into Minnesota, with some areas in both states averaging 3-5°F above normal (Figure 3). However, the mean temperature did actually come in at 0.9°F and 0.1°F below normal in both Iowa and Minnesota, respectively.

Rain for the Lakes, and None Elsewhere

Rain was not a common sight across the Midwest this past week, and some western parts of the region received little to no rain. Most of Minnesota, Iowa and Missouri averaged less than 0.01 inches of rain, and areas of those states west of I-35 largely saw nothing (Figure 4). This means those states came in at over an inch below normal for the week (Figure 5). Areas east of I-35 in these states saw precipitation between 5 and 10 percent of normal for the period, whereas western areas of Iowa, Minnesota and Wisconsin saw 0 percent of normal precipitation (Figure 6). Compare this to most of Michigan and southeastern Wisconsin, which saw 175 to 200 percent of normal precipitation.

Drought Expansion For Most, Relief for Few

Parts of the region have spent the summer in a worsening drought. While the cooler temperatures may have helped crops, the lack of rain did not. This is especially the case for Iowa, Wisconsin and Minnesota, which saw drought continue to grow or persist this past week, especially in the D2-D4 (Severe to Exceptional Droughts) categories (Figure 7). Extreme drought (D3) was slightly expanded in southwestern Wisconsin, southeastern Minnesota, and northern Iowa. Exceptional drought persists in far northwestern Wisconsin along Lake Superior. Large chunks of these states continue to remain in severe drought (D2). However, thanks to the aforementioned above-normal rainfall in Michigan, abnormally dry conditions were wiped out for most of the state.

Record Maximums and Record Minimums

Drought expanded, but the abnormally cool temperatures early in the week were great for doing outside work. Dozens of record low maximum temperatures were set across the Midwest (Figure 8). On August 15, Fort Wayne, Indiana had its coldest August 15th on record, with a record low maximum of 69°F. On the same day, Fond du Lac, Wisconsin and Lake Geneva, Wisconsin also had their coldest August 15th on record, with record low maximums of 64°F and 67°F, respectively.

Despite the record low maximum daily temperatures to start the week, temperatures and dew points skyrocketed by the end of the week. Iowa, Missouri, Illinois and Indiana took the brunt of the heat, with most of the record daily high temperatures in those states (Figure 9). Joplin, Missouri broke the daily record high maximum temperature on August 20, with an observation of 101°F. Des Moines, Iowa recorded a low temperature of 76°F on August 21 which was the highest recorded minimum temperature for that date.

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