The start of meteorological fall was pretty typical in terms of temperatures across the entire Midwest with most areas near normal or just 1-2 degrees above normal. The month as a whole was pretty inactive in terms of severe thunderstorms, with only 1 day of severe weather in Dayton and Columbus. Thanks to the decrease in storms, precipitation amounts were down significantly in Indianapolis, Dayton and Cincinnati where Indianapolis received only 0.12” for the entire month! The opposite occurred in Chicago and Columbus where these areas saw average to above average precipitation totals for the month. The winner for most rainfall was Chicago O’Hare airport, where 4.3” of rain occurred, which is 1.46” above their normal. Overall, it was a pretty lackluster start to fall in terms of flooding rain and severe storms but soon enough we’ll be talking about snow! If you have not renewed your winter services for this upcoming winter please do by October 31st before your account goes inactive!
Drought monitor image from the Department of Agriculture.
Despite September 1st marking the start of meteorological fall, the beginning of the month felt more like summer with temperatures in the 80s. These above average temperatures were accompanied by showers and periods of rain, with the brunt of the rainfall remaining confined to Cincinnati, Columbus, and Chicago, while Indianapolis and Dayton saw only a few hundredths of an inch. After some seasonable warm and dry days, a strong low-pressure system swung through the Midwest between the 6th and 8th. This led to 1-3” of rain in Columbus, creating some areas of poor drainage and roadway flooding with a few streams and creeks overflowing their banks. In addition to the minor poor drainage flooding, a few of these storms became severe in Dayton and just north of Columbus. 10 wind damage reports followed, with multiple large trees down as well as powerlines due to gusts up to 70 mph! The winds were so strong it blew over a barn!
After this stretch of active weather, warm and dry conditions (temperatures in the upper 80s to near 90 degrees) redeveloped for the Midwest between the 9th and 13th. One exception was in Chicagoland, where temperatures were only in the upper 60s to lower 70s with pesky rain showers. Then, a dry cold front pushed through the Midwest on the 14th, causing temperatures to plummet back into the 70s. This front led to a pattern change across the Midwest where below average temperatures and dry weather took control. Between the 15th and 27th, temperatures were generally in the 70s, and with no substantial rain, abnormally dry to moderate drought conditions formed across the Midwest. Central Indiana featured the most significant of the drought conditions. Interestingly, the filtered sunshine seen over this period wasn’t due to high clouds, but was actually from abundant wildfire smoke from West Coast wildfires that got lofted into the upper atmosphere.
Western U.S. wildfire smoke circled in red across the Midwest 9-14-2020. Courtesy NOAA.
The dry stretch of weather came to a close by the end of the month (28th – 30th) when a series of disturbances rotated through the region. Over the three-day span, between 0.25 - 1.00” of rain fell across the Midwest, except for Indianapolis where only 0.08” of rain fell (67% of their monthly rainfall). In addition to the rain, wind gusts as high as 55 mph led to some debris and lawn furniture being tossed. Overall, the lack of precipitation led to the driest September on record for Indianapolis and tied for the 4th driest month since 1871!