Midwest Overview - October, 2004

---

Temperatures in October were generally near to above normal across most of the Midwest, ranging from 1F below normal in the central Midwest  to 1.5F in most other areas.  The exception was an area from southern Missouri through Kentucky, which averaged 2.5F to 4.5F above normal (Figure 1).  This area marked the mean position of the southern extent of the advance cold fronts (of which there were many) that moved through the Midwest this month.  For the most part, the more active weather pattern in October more than made up for the precipitation deficits that accumulated during September.  There were two distinct areas of heavy precipitation, one in the southern and central Midwest and another in the far northern Midwest (Figure 2).  Precipitation in these areas was generally 150 to 200 percent of normal .  The notable exceptions were in western Iowa, where precipitation ranged from 25 to 50 percent of normal,  and from the southern tip of Lake Michigan across northern Indiana, southern Michigan, and northern Ohio where precipitation was 50 to 75 percent of normal.


Cold Beginning

The mild and dry weather of September continued into the first few days of October, but that's where the resemblance to September weather ended.  The growing season came to an end the first week of the month as far south as the Ohio Valley as a series of cold fronts swept through the Midwest.  In many areas the first freeze of the fall was as much as two weeks early.  The cold fronts did bring some rain to the region, especially from southwestern Missouri into southern Iowa.  The greatest departures from normal the first half of the month were centered over northeastern Missouri and extended over the central Midwest. (Figure 3), and ranged from 2F to 4F below normal..  The warmest weather occurred over northern Minnesota and Wisconsin as well as southern Kentucky, with temperatures 1F to 3F above normal.  Significant rain came to much of the Midwest in the October 11-17 period as the remnants of Tropical Storm Matthew lifted northeastward through the Ohio Valley.  The first half of the month was marked by the first heavy snow of the season in the western Michigan UP.


 Warm, Stormy End

The cool weather the first half of the month reversed for the last half, and temperature departures ranged from near normal in northwestern in northwestern Minnesota to 8F above normal in southern Kentucky (Figure 4).  A series of weather systems cross through the Midwest the last half of the month, warming the weather on their approach but only cooling slight after their passage.  More frequent south and southwest flow drew ample moisture into the Midwest. This helped fuel showers and thunderstorms with the frontal passages.  There were a number of severe weather occurrences the last ten days of the month, the most active of which was on October 29 when as many as five tornado watches were in effect for parts of the Midwest.  The regular and often heavy rain through the end of the month delayed completion of the corn and soybean harvest in much of the region.