August 2010
Midwest Overview - August 2010
Warm August Temperatures
August was warm across the Midwest
(Figure 1). Temperatures were 2° to 5°F above normal across the region. Daily temperature record totals showed a strong tilt towards record highs with over 1000 record highs and fewer than 100 record lows (Figure 2).
August Precipitation Varies Widely
Precipitation for August varied considerably across the Midwest. Departures from normal ranged from 3" below normal up to 5" above normal
(Figure 3) The heaviest rains were grouped in three location, southern Kentucky, central and southeast Iowa, and central Minnesota into northwest Wisconsin. Dry areas receiving less than 50% of normal precipitation included southern Missouri, southern Indiana, and southern Michigan (Figure 4). More than 650 daily precipitation records were set during the month with over 90 records on the 14th and 21st, more than 60 on the 9th and 11th, and 20 or more on nine additional days
(Figure 5). Drought eased slightly in the upper Midwest but conditions degraded across the southern and eastern parts of the region (Figure 6).
Summer Temperatures Slightly Above Normal
Temperatures averaged slightly above normal for most of the Midwest
(Figure 7). Departures were close to zero in the northwest parts of the region and increased to 4°F above normal in parts of Kentucky and southern Missouri. Each of the three summer months was warm across the Midwest with the exception of Minnesota in June. The persistently warm conditions, especially in the southern and eastern parts of the Midwest contributed to the development of abnormally dry and drought conditions in those locations (Figure 8).
Summer Precipitation Above Normal for Most of the Midwest
Most of the region had above normal precipitation for the summer months
(Figure 9). Drier than normal conditions extended across southern Missouri and up the Ohio River valley. Wetter than normal conditions were the rule across much of the remaining areas in the Midwest. A swath extending across Iowa, from northwest to southeast, and into northeast Missouri and west central Illinois received more than 200% of normal for the three month period. Rainfall totals in central and southeast Iowa exceeded 30" for the season (Figure 10). La Crosse, Wisconsin
(La Crosse County) recorded its wettest summer with 20.93" and state-wide Iowa ranked as the second wettest summer with 23.23".
A Busy Year for Tornadoes in Minnesota (and Wisconsin too)
2010 was a busy year for tornadoes in Minnesota. Preliminary numbers showed Minnesota leading the nation in tornado count. Although many tornadoes were yet to be confirmed by damage assessments, it was likely that Minnesota would easily pass the previous state record of 74 tornadoes set in 2001. The twisters in Minnesota were not just numerous but also strong. The state reported its first EF4 tornado since 2000 when three different EF4 tornadoes touched down on June 17th, 2010. Three Minnesota tornadoes of that severity had not occurred on a single day since 1967. Wisconsin also recorded one of its busiest years and will likely rank as its third busiest year for number of tornadoes. Iowa on the other hand had a relatively quiet year for tornadoes, though a few were strong storms. Tornado fatalities were recorded this summer in Illinois (1), Ohio (7), Minnesota (3), and Michigan (1).
Iowa Flooding
High water has been a summer long battle for Iowa residents. The heavy rains that fell across the state pushed numerous rivers above flood stage and pushed some reservoirs over spillways. Iowa precipitation was both persistent, with few long dry spells, and heavy, with numerous downpours from several inches up to 12". The last two weeks of August gave Iowa welcome relief from the rains and allowed rivers to drop bank into their banks.
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