How often does September have a day that produces a higher temperature than August, like this year?

Dear Tom,
How often does September have a day that produces a higher temperature than August, like this year?
— Robert Pechous, Wheaton
Dear Robert,
It happens more often than you think. This September has already produced a high of 95, while the best that August could muster was just 90. We had Chicago climatologist Frank Wachowski scan the records, and he found that since 1871, September has posted a higher temperature than August in 27 of 147 years, or more than 18 percent of the time. More surprisingly, Wachowski found eight years when September hosted the highest temperature of the entire year, most recently a 94-degree high on Sept. 2, 2008. The all-time record high for September is 101 degrees logged Sept. 1-2, 1953, readings warmer than August but falling short of the year’s highest, a high of 104 on June 20.
This September has already produced a high of 95, while the best that August could muster was just 90.
Ask Tom, Tom Skilling, Chicago weather, WGN weather