Midwest Overview - October, 2005

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A Very Warm Start, A Cold End

A pattern of southwesterly flow aloft allowed summer-like weather to continue through the first half of October with several days of warm and unusually humid weather (Figure 1).  Temperatures were well above normal,  with average daily temperature departures as much as +8°F in northern Michigan (Figure 2).  However, it was clear that autumn and winter were not far behind when a rapidly intensifying storm moved out of the Northern Plains and into the northern Midwest the first week of the month.  The storm produced blizzard conditions in the Dakotas, snow in northwestern Minnesota, and torrential rains in central Minnesota and northwestern Wisconsin.  The cooling behind the storm was temporary, and mild conditions returned to the Midwest   The weather pattern changed markedly the third week of October as a trough of low pressure became established over the eastern U.S. (Figure 3).  This pattern produced northwest flow over the Midwest,  and the result was two weeks of colder than normal weather.  Temperatures the last two weeks of the month ranged from 3°F to 4°F below normal in eastern portions of the region to 2°F to 3°F above normal in northwestern Minnesota (Figure 4).  Temperatures for the month were near normal across much of the Midwest, and 2°F to 3°F above normal from northern Wisconsin across the Michigan Upper Peninsula and northern lower Michigan (Figure 5).

Extended periods of dry weather during the month allowed harvest activities to proceed at full speed, and by the middle of October both corn and soybean harvests were ahead of the 5-year averages in most areas.   Precipitation was well above normal across Minnesota and Wisconsin, largely as a result of the storm the first week of the month (Figure 6).  Precipitation was also above normal across most of Ohio, and near normal across northern Missouri.  The remainder of the region received 50 percent or less of normal of normal October rainfall, with southern lower Michigan the driest area with less than 25 percent of normal precipitation.  Detroit, MI recorded only  0.13 inch of rain during October, making this the driest October on record and the second driest month ever.  The previous record of 0.30 inch was established in 1892.  The record driest month in Detroit is February 1877 when only 0.04 inch of precipitation was observed.  Flint, MI received only 0.33 inch of rain this month, tying the record driest October (first set in 1944).   A cold front produced a large area of rain across the southern half of the region on October 31, but those totals are not reflected in the October statistics.   (Note: The rain that occurred on October 31 is reported on November 1). Moderate to Severe drought conditions persisted in parts of Iowa, northern Illinois, and southern Wisconsin.  With the growing season now over, drought impacts will be mostly hydrological.