If this September has felt warmer than usual, it's because it has been. In fact, it's been one of the warmest in Chicago on record. According to a report from AccuWeather, the average daily temperature in Chicago this month has been 4.5 degrees above the historical average of 64.6 degrees.
The warmest September in Chicago's recorded history was in 1931, when the average daily temperature was 71.2 degrees. The year 2015 could top that mark, but with a cold front set to move in on Tuesday that doesn't seem likely.
Reports this summer of a record-breaking El Niño have suggested that Chicago, as well as the rest of the Midwest, is in for a mild winter. A warmer-than-average September doesn't necessarily validate that prediction, but we'll take all of the nice weather we can get. After the last two devastatingly cold winters, Chicago deserves something nice from the gods.