Midwest Overview - May, 2004

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May 2004 was a record wet month in the Midwest, with the precipitation average for the 9-state region (IL, IN, IA, KY, MI, MN, MO, OH, and WI) of 7.15 inches, or about 0.77 inches more than the previous record May since 1895. Individually, the states of Michigan and Wisconsin also set new statewide precipitation records for May since 1895 by more than 1 inch of rain total. The core of the wettest region stretched from northeastern Iowa through southern Michigan, with peak totals exceeding 12 inches in places (Figure 1). A very broad band along axis exceeded 200% of normal precipitation, with some regions receiving 300%, or three times, the amount normally received in May (Figure 2). Much of the precipitation occurred along a quasi-stationary boundary that oscillated back and forth across the central latitudes of the Midwest, leaving the southern part of the Midwest warmer than normal and the northern part colder than normal. The warmest temperatures were in the southeastern part of the Midwest, +4-6°F, and the coldest temperatures in the northwestern Midwest, -6-8°F (Figure 3). A number of major severe weather outbreaks were featured during May, especially in the second half of the month.