Midwest Weekly Highlights - May 25-31, 2004

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More Severe Weather and Heavy Rain in the Midwest

The last week of May was even more violent than the previous week. Every day from the 25th to the 31st had severe weather reported in some portion of the Midwest, including several days with widespread outbreaks. Almost all of the Midwest recorded more than one inch of rain for the week (Figure 1), while central and eastern Kentucky received more than five inches of rain. Almost all of the Midwest received more than 200% of normal precipitation during the last week of May (Figure 2), with totals exceeding 500% of normal in Kentucky, resulting in serious flash flooding over a large area and moderate river flooding in places. Much like the previous week, temperatures were 4-8°F cooler than normal in the northern Midwest, and 4-6°F warmer than normal in the southern Midwest (Figure 3). The rain this week finally put to rest any current drought concerns in the Midwest, with only some portion of north and central Minnesota retaining some long term residual dryness (Figure 4, National Drought Mitigation Center).

Record Wet March

The 9-state Midwest region (Illinois, Indiana, Iowa, Kentucky, Michigan, Minnesota, Missouri, Ohio, and Wisconsin) set a new record for precipitation during May of 7.13 inches, exceeding the previous record May of 1943 by 0.77 inches. May 2004 is the second wettest month overall since 1895, exceeded only by the 7.15 inch regional average during September 1926. Michigan and Wisconsin individually received record May precipitation amounts. Michigan’s 6.82 inches exceeded the previous record of 1912 by 1.04 inches, while Wisconsin’s 7.76 inches exceeded the previous record May in 1918 by 1.01 inches. Kentucky had the largest May average rainfall in the Midwest, 9.02 inches, but this was only the third wettest May since 1895. Iowa and Ohio also had their third wettest May, while Minnesota had its fourth wettest and Illinois had its eighth wettest. The “driest” states in the Midwest, relative to past May records, were Indiana (11th wettest) and Missouri (23rd wettest). While the precipitation in the Midwest was widespread, it was especially heavy in two bands, one focused on the persistent frontal boundary through the north-Central Midwest, and the other through the southern Midwest (Figure 5). Only a tiny corner of southwest Missouri was below normal for May (Figure 6), while the northern half of the Midwest received well over double the normal precipitation amount.