August 2021 Climate Summary

August 2021 Climate Review:  Temperatures finished the month anywhere from 0.5 to 1.5 degrees above normal.  While average high temperatures were generally within a degree of normal, average lows ended up around 1.5 to 2 degrees above normal, which was likely a function of higher humidity and above normal precipitation across much of the area.  The month started out cooler than normal as a refreshing air mass built into the region in the wake of a series of cold frontal passages at the beginning of the month.  By its second week, August started to feel more like the August we’re accustomed to as highs topped the 90 degree mark for a handful of days from August 9-12.  Lows were also quite muggy during this period, highlighted by the record warm low temperature of 77°F set at Cape Girardeau and Poplar Bluff and tied at Paducah on August 10.  Temperatures once again dropped back into the 80s for highs and 60s for lows during the middle of the month following the passage of a cold front on August 15.  In fact, both Cape Girardeau and Poplar Bluff tied their record cool high temperatures for August 18.  However, the cooler weather wouldn’t last, and was ultimately followed by a week long period of excessive heat as highs topped 90 degrees and heat index readings surged past the century mark during the last full week of the month.

In typical summer fashion, August precipitation totals varied widely across the region, ranging from about 1.5 inches below to 4 inches above normal depending on the location.  Rainfall totals for August averaged above normal across much of southeast Missouri and western Kentucky, with another band of above normal rainfall along the Interstate 64 corridor from south central and southeast Illinois into southwest Indiana.  However, not everyone shared in the wealth.  Most notably, rainfall totals in the middle part of the region were well below normal, particularly across portions of southern Illinois.  In fact, parts of Jackson, Williamson, Franklin, and Union counties in Illinois only picked up 1 to 2 inches of rainfall during the entire month.  Contrast that to the 6.74 inches of rainfall at Evansville, which made for the 7th wettest August on record.  And our CoCoRaHS observers in Reidland, KY, Poplar Bluff, MO, and Albion, IL accumulated even more than that.  The cooperative observation site at Wappapello Dam had the highest precipitation total of the month at 7.92 inches.