August 2017
Monthly Overview - August 2017
Cool August
August temperatures were below normal across nearly all of the Midwest
(Figure 1). Only a few areas in Ohio had temperatures near normal. For the region as a whole, temperatures averaged 68.1°F which was 2.8°F below normal. This was tied for the 14th coldest August for a record extending back to 1895. Missouri and Iowa ranked among the ten coldest August’s on record (1895-Present). Nearly 500 combined daily low maximum and low minimum temperature records were broken or tied in August in the Midwest (Figure 2). Many of these records occurred during a very cool stretch from August 4-8. Temperatures dipped below freezing at several stations in the U.P. of Michigan and Minnesota Arrowhead for the first fall freeze of the season on the morning of August 25
(Figure 3). This was near the earliest fall freeze on record for these areas (Figure 4).
Near-Normal Precipitation
August precipitation in the Midwest was largely limited to Minnesota, western Iowa, Missouri and Kentucky as dry conditions prevailed across most of the central Midwest
(Figure 5). Region-wide, the Midwest had 3.80 inches (96.5 mm), which was 0.14 inches (3.5 mm) above normal. Areas of southwestern Minnesota, and western Missouri had more than twice the normal amount, while western Iowa, eastern southeastern Kentucky, northeastern Minnesota and the U.P. of Michigan had less than 75 percent of normal (Figure 6).
Summer of Extremes
While the average of June through August temperatures and precipitation were close to normal, many extreme fluctuations occurred across the region. For the summer, the Midwest was slightly cooler than normal
(Figure 7). Region-wide temperatures for June through August averaged 70.6°F which was 0.6°F below normal. However, many extremes were observed on both the cool and warm ends of the spectrum. More than 1,500 daily low and high temperature records were broken or tied across the region from June through August. Precipitation for the June through August period was 11.98 inches, which was 0.02 inches above normal (Figure 8). However, many precipitation extremes occurred. Portions of Iowa, central Illinois and southern Lower Michigan had less than 75 percent of normal, while areas in Missouri, Ohio, Wisconsin and the U.P. of Michigan had more than 125 percent of normal
(Figure 9). Rainfall often fell in extreme amounts with extended dry periods in between. More than 1,200 daily precipitation records were recorded in the June through August period, with at least 300 in each month.
Drought Persists
Drought persisted across western Iowa and northwestern Minnesota in August and worsened in southern Iowa in August (Figure 10). Drought coverage across the Midwest remained at less than 9 percent during the month. Extreme drought was added to several counties in south-central Iowa during the middle of August. Moderate drought was also added in central Illinois along with an expansion of abnormally dry conditions in southern Lower Michigan.
Total Solar Eclipse
The August 21 total solar eclipse traversed across several Midwest states
(Figure 11). This was the first total solar eclipse in the Midwest region since 1925. Viewing of the eclipse along the path of totality was unobscured for most, as fair weather cumulus clouds decreased as solar radiation decreased. However, storms associated with a frontal boundary obscured viewing of the partial eclipse in Iowa, Minnesota, Wisconsin and northern Illinois.
Severe Weather
Severe weather occurred on 22 of the 31 days in August in the Midwest (Figure 12). However, only one day, August 18, had more than 50 storm reports. More than a dozen weak tornadoes were observed in Minnesota, Iowa, Illinois and Ohio from August 16-18. No injuries were reported with any of these tornadoes, though livestock were killed and crops were damaged from an EF-2 tornado in southwestern Minnesota on August 18.
-BJP-