Average Temperature Departure May 1-15 Average Temperature Departure May 16-31
Total Precipitation March-May 2010 Statewide Ranks

Midwest Overview - May 2010

May Features Improving Growing Weather

Planting of corn and soybeans was well ahead of normal at the beginning of May, but as the month started producers were concerned about the development newly emerging corn. Much cooler than normal weather held over most of the corn and soybean belt the first two weeks of the month. Average daily temperatures the first half of the month were from 2°F to 3°F above normal along and south of the Ohio River. However, temperatures northwest of the Ohio River were from near normal from southwestern Missouri through central Illinois and Indiana, falling off to 6°F to 8°F below normal in western Iowa and Minnesota (Figure 1). The second half of the month saw little change in the Ohio Valley, but temperatures in the remainder of the region were near to much above normal (Figure 2), as much as 10°F above normal in the eastern Michigan Upper Peninsula. When all was said and done at the end of the month, temperatures ended up near normal along and west of the Mississippi River, and 2°F to 4°F above normal east and north (Figure 3).

During the last week of May, 29 locations in the Midwest recorded their highest daily maximum temperatures for the month, including 97°F at Cambridge, OH on May 29.


Most of the region received normal to well above normal precipitation in May with the exception of a band from western Iowa northeastward across the Upper Peninsula of Michigan (Figure 4). Precipitation in this band was generally only 50 to 75 percent of normal. The area of Extreme Drought depicted on the U.S. Drought Monitor in northeastern Wisconsin and the Michigan U. P. expanded by the end of the month. In contrast, precipitation over northwestern Minnesota and much of Kentucky was twice normal. Thunderstorms that caused widespread flooding in Tennessee on May 1 extended into Kentucky dropping five to ten inches of rain in two days. The record-breaking rainfall was quickly followed by historic flooding along many rivers in Kentucky that in some cases took weeks to fall below flood stage. The two-day storm shattered one- and two-day rainfall records in many places and monthly totals approached all-time records for May. Recurrence intervals across south-central Kentucky were estimated to be as high as 200-years for counties along the Tennessee border. Bowling Green was hardest hit with 10.14” received at the Warren County Mesonet station. Nearly five inches of rain fell each day in Bowling Green which ranks as the 6th (4.92”) and 8th (4.75”) highest daily rainfall totals since 1900. This storm was notable in that while most of the previous one- and two-day record rain events in the region were produced by systems that were tropical in origin, the May 1-2 storm was extratropical in nature. At least five people were killed across central Kentucky and damage estimates surpassed $30 million.

Snow fell in the upper Midwest the first week of May, with as much as five to seven inches in the Michigan U. P. The snow and cold weather in the upper Midwest caused serious damage to the ginseng crop in northern Wisconsin, with estimates that 80 to 90 percent of the 1,400 acres of crop was destroyed or damaged.

Spring Season Very Warm, Variable Precipitation

The spring season (March, April, May) in the Midwest ranked in the top five warmest for six of the nine Midwestern states, and it was the warmest on record for Michigan (Figure 5). Spring average temperatures ranged from 1°F above normal in much of Missouri to 5°F to 6°F above normal from northern Minnesota southeastward to northern lower Michigan (Figure 6). Spring precipitation was normal to above normal from Missouri into the southeastern half of Iowa, northwestern Illinois, and across northern Indiana and southern lower Michigan (Figure 7). Precipitation was 150 to 200 percent of normal across northwestern Minnesota. In contrast, precipitation was less than 50 percent of normal across the Upper Peninsula of Michigan.

The Kentucky Climate Center also contributed to this report.

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