Another Rain Surplus for the Midwest: June 2017
June 2017 came in as another wet month for the Midwest. The typical hot and stifling weather that the central United States can often see in June was held in check for at least another month, though bouts of it were felt throughout the period. This was thanks, partially, to the ample rainfall activity, which found its way into the record books quite a few times.
Outside of run-of-the-mill summertime thundershower activity, the first two weeks of June were relatively quiet across the Great Lakes and Ohio Valley. For some, this was the hotter half of the period, contrary to what one would typically expect approaching the heart of summer. This was glaringly true for Chicagoland, which observed a large difference in overall temperatures between the periods of the 1st thru the 17th, and 18th thru the 30th. While highs during the first half of the month were 4 - 6 degrees warmer than average (O'Hare averaged 86.1 degrees), the second portion was 6 to 8 degrees cooler (79.6 degrees) than the first half of the month. While this was not as extreme in the Ohio Valley from Indy through Columbus, it still turned out to be at a bit cooler than normal to close out June.
The cooler periods experienced throughout the month were largely attributed to an active, rainy pattern, which was thanks to a stubborn trough over the eastern US, and a large hot and dry ridge which dominated the west. The result was a larger than normal influx of summertime disturbances, resulting in many days with measurable rainfall. Several of the storms even broke records for most of the Corn Belt’s major cities.
The most significant event occured toward the tail-end of the month in northern Illinois. This was courtesy of a strong disturbance making its way into Wisconsin with a trailing cold front, bringing rounds of heavy thunderstorms, in some cases repeatedly hitting the same areas and leading to significant totals. Amongst the highest totals was Rockford. A measurement of 4.11” of liquid not only smashed the record for the date, but nearly came in first as the wettest calendar day ever in June for the city. It in fact was the second highest 1-day total on record for June, falling just shy of the 4.20” that was recorded in 2009.
Dayton came in with a pair of record-setting rain events itself. A grand total of 2.68” on the 14th bested an old record of 1.26” in 1996, while another storm system dumped 2.86” of rain on the city on the 23rd to get the better of a 1.06” event going all the way back to 1896! These individual events were enough to bring a rainfall surplus for the month across much of the Midwest, with some spots finishing 1 to 3” above normal.