Temperature and Precipitation Anomalies. The Midwest once again experienced a split precipitation pattern, with the jet stream dipping into the northwest Midwest frequently and bringing well above normal amounts of precipitation to that area. The southeast Midwest, on the other hand, was dominated by an extension of a ridge from northeast Canada much of the time, and was drier than normal again. The remainder of the region was close to normal. The northwestern two-thirds of the Midwest received more than 4 inches of rain, while much of southern Minnesota, northwestern Minnesota, and northwestern Iowa received 6-10 inches (Figure 1). Minnesota had its 3rd wettest August in 108 years, and completed its all-time wettest summer with a state average precipitation total of 17.61 inches. This total even exceeded 1993, the year of great Midwestern floods. On the other side of the Midwest, large areas along the Ohio Valley received less than 50% of normal precipitation (Figure 2). Ohio had its 14th driest August to complete its 7th driest summer. Temperatures were up to 2°F below normal in the rainy areas of the northwest Midwest, while temperatures were 2-4°F above normal in the dry Ohio Valley (Figure 3). Overall, the Midwest had its 18th wettest and 29th warmest August. Soybeans were aided by rains along the Corn Belt, but the added rain only marginally affected corn at this time of year. Drought began to intensify in the Ohio Valley towards the end of the month, and spread into more of eastern Ohio and Kentucky (Figure 4, National Drought Mitigation Center - NDMC).

Extreme Events and Impacts.

August 11-13, 2002: Strong Storms Develop Along a Slow Moving Cold Front.
Most of the rain during the second week of August during the advance of a very slowly moving cold front that was still crossing the Midwest on the 13th. Substantial rain first fell in northern Iowa / southern Minnesota (Figure 27, NWS) and in central Wisconsin (Figure 28, NWS) on the 11th and 12th. On the 12th and 13th, rain fell all along and east of the front as it moved through Iowa, Missouri, Illinois, Wisconsin, and Michigan. Southwestern Iowa, northern Illinois, and southern Wisconsin where either in drought or abnormally dry, and the rain was quite helpful for crops. The strongest line of storms moved through southern Wisconsin on the evening of the 12th (Figure 29, NWS), leaving considerable damage in its wake and 20,000 customers without power in the Milwaukee areas. Flash flooding also resulted, as up to 7 inches of rain fell in some locations in southeastern Wisconsin (Figure 30, NWS).

August 16 and 19, 2002: Multiple Flash Flood Events in the Central Midwest. A stationary front sagged across the central Midwest during the third week of August, bringing general light rains but also triggering tremendous downpours in spots where storms trained over and over. Heavy rains were centered on the southeast Iowa - central Illinois axis on the 15th and 16th, bringing up to 6 inches of rain to these areas and causing flash flooding (Figure 31, NWS). On the morning of the 16th, Lincoln, IL, set an all time record for any single day of August of 4.22 inches. Heavy rains also occurred further north, where Minneapolis set a new daily precipitation record of 1.87 inches on the 16th. Strong storms also disrupted the PGA golf tournament, and caused power outages and local flash flooding. The biggest rain event of the period, though, occurred when the front moved south late on the 18th and early on the 19th, letting loose large training thunderstorm clusters (Figure 32, NWS) before forming a squall line to sweep southward (Figure 33, NWS). Amounts of precipitation ranging from 4-8 inches fell over a wide area of central-east Illinois and central-west Indiana (Figure 34, NWS). At the Urbana, IL, location of the MRCC, 3.02 inches of rain were recorded on the 19th. Linden, IN, received 5.22 inches of rain on the same day. Widespread flash flooding and urban street flooding took place throughout the central Midwest.

August 21-22, 2002: Historic Rain Event in NE Iowa and N Illinois.
A tremendous rain event hit eastern Iowa and northern Illinois on August 21-22. A strong upper level disturbance moving along a stationary front in the central Midwest caused widespread rain totals of 4-8 inches in northeastern Iowa and northern-most Illinois, with some locations receiving more than 10 inches. National Weather Service Radar from Davenport (Figure 35, NWS) and Chicago (Figure 36, NWS) recorded a band of rain with radar estimates exceeding 12 inches in places. Dubuque, IA, set its all time 24 hour precipitation record with 8.96 inches. Some locations in Illinois received more than that, with 9.12 inches recorded at Freeport, 10.13 inches at Stockton, and 11.69 inches at Galena. All of these totals easily exceed the 100-yr return interval for both 24-hour and 48-hour precipitation totals in the region. Yet, due to the dryness experienced early in the summer, stream and river flooding was minimal after the initial flash flooding had taken place. Only the Marquoketa River in Iowa exceeded major flooding levels for a day. River levels were still at record highs for the time of year (Figure 37, U.S. Geological Survey), but most of these record highs were lower than major flood level, as rivers are usually quite low in late August. Some crop damage occurred, although the strongest winds and greatest damage were north of the heaviest rain, occurring mostly in southern Wisconsin (Figure 38, Storm Prediction Center). A 98 mph gust from a microburst was measured at Waukesha County Airport. About 56,000 in the Milwaukee, WI, area lost power, 38,000 lost power at Rockford in northern Illinois, and there were many scattered outages elsewhere.

As the front finally moved forward on the evening of August 22, even more storms were unleashed. Added to earlier rains, totals in parts of north-central Illinois reached over 5 inches (Figure 39, NWS). On this day, the Des Moines, Iowa area was hardest hit, with 50,000 customers losing power when 75 mph wind gusts entered the area around 5:30 AM. Straight-line winds caused extensive tree loss, with clean-up expected to continue through mid-September. Public schools had to use a "snow day"; and cancel classes due to damage and flooded streets preventing children from safely going to school. At 7 PM, 8,000 still were without power. Further south, in Willard, IA, a normal strength thunderstorm tragically struck a funeral party with lightning. Three people died and one was critically injured as lightning hit a nearby tree. Lightning also started a fire at St. John's Episcopal Church in Quincy, IL, destroying most of the 19th century cathedral.