Precipitation: From Too Much to Too Little
Incredible precipitation differences impacted the Midwest during August, ranging from historic flooding to severe drought. Some locations in the central Midwest reported no measurable rainfall, making it their driest August on record, while portions of Missouri witnessed their wettest August on record with some locations reporting over 15" of rainfall for the month (Figure 1). These totals were anywhere from 5" below normal to over 8" above normal (Figure 2). Outside of the areas with extremely wet or dry conditions, much of the Midwest was below normal in terms of precipitation. There were over 375 daily precipitation records, two of which also broke all-time precipitation records.
During the first part of August, a stationary front draped across the southern Midwest brought a prolonged period of exceptional precipitation to portions of Missouri, southern Illinois, and Kentucky. In Missouri, over a foot of rain fell throughout August in several locations, the highest of which was 20.25" in Richland, MO (Pulaski County). Other high monthly rainfall totals include 17" in Fort Leonard Wood, MO (Pulaski County), 16.86" in St. Robert, MO (Pulaski County), and 15.44" in Hazelgreen, MO (Laclede County). These heavy precipitation events throughout the early part of August caused major flash flooding issues across the southern Midwest, including three flood-related fatalities in Missouri. To read more, visit the weekly highlights from August 1-7 and August 8-14.
Record low monthly precipitation was the story in other parts of the Midwest. Based on preliminary state data, Illinois experienced its 3rd driest August on record, Indiana its 4th driest, and Iowa and Minnesota their 7th driest. Some stations recorded no measurable precipitation throughout the month, making it the driest August on record, including Mt. Pleasant, IA (Henry County), Keokuk, IA (Lee County), Burlington, IA (Des Moines County), Fort Madison, IA (Lee County), Kirksville Regional Airport, MO (Adair County), and Edina, MO (Knox County).
Cool Start and Warm Finish to August
August temperatures averaged within a couple degrees of normal across a majority of the Midwest (Figure 3). However, the near normal temperatures are masking the fact that the first half of August was dominated by unseasonably cool temperatures across the region (Figure 4), while the second half was dominated by unseasonably warm temperatures, especially in Minnesota (Figure 5).
The unseasonably cool first half of the month even resulted in the first 32°F reports in the region in northern Minnesota and northern Michigan on August 10th and 14th (Figure 6), which falls within the earliest 10th percentile of first fall freeze events climatologically over the last 30 years
(Figure 7). The unseasonably warm stretch of temperatures later in the month brought record breaking high temperatures to Minnesota, including 97°F in Red Lake Falls, MN (Red Lake County) on August 20th, which was 18°F above the normal maximum temperature for this day. There were over 880 temperature records throughout August, with record lows dominating the first half of the month and record highs the second half.
Flash Drought Development and Impacts
The lack of precipitation in some portions of the Midwest during August resulted in the rapid expansion of drought (Figure 8). At the start of September, over 28% of the region is designated as either moderate (D1) or severe (D2) drought, compared to only 2% at the beginning of August. The areas impacted by severe drought include central Iowa, northern Missouri, extreme western Illinois, western Wisconsin, and central Minnesota. Michigan, Ohio, and Kentucky are currently the only states in the region that are drought-free.
The milder temperatures at the beginning of the month helped crops endure the start of the prolonged period of unusually dry weather in portions of the Midwest. However, with the heat returning in the second half of August, crops began to deteriorate rapidly. As of September 1st, nearly a quarter of the corn crop in Iowa, Missouri, and Wisconsin are in very poor to poor condition according to the USDA Crop Progress Report. Despite the recent deteororiation in corn condition in some states, much of the corn crop throughout the Midwest remains in fair, good, or excellent condition (Figure 9).
Summer 2013 Summary
Summer temperatures (June-August) averaged within a couple degrees of normal across the region, with slightly below normal temperatures in portions of the southern and central Midwest and slightly above normal temperatures in northern Minnesota and northern Michigan (Figure 10). Summer precipitation was well below normal (25% to 50% of normal) for much of Iowa, western Illinois, and northern Missouri (Figure 11). On the other hand, much of the southern and eastern Midwest experienced summer precipitation that was 125% to 175% of normal. In fact, Kentucky and Ohio experienced their 3rd and 5th wettest summer on record, respectively.