September – Warm and Dry in Illinois

Strictly speaking, we are not done with September until the end of today. However, I went ahead and pulled together the September statistics because there is no rain in the forecast. All these statistics are based on data that have come in so far and may change slightly in the coming weeks.


The statewide precipitation for September was 1.87 inches, 1.39 inches below average and the 14th driest September on record. As the first two maps below illustrate, dry conditions were widespread. Only a few spots received 3 or more inches in Illinois, including the Chicago area, far western Illinois, and the southeast corner of the state. Several areas in the state received less than an inch of precipitation.

The second map shows the September data as a percent of average. Several areas had less than 25 percent of average (red). Even the “wet” areas had trouble achieving totals close to the 1981-2010 average. Overall, the precipitation departure for September was 57 percent of average.

This is the 6th driest July-September on record for Illinois with 6.64 inches (4.24 inches below average). Ironically, this came on the heels of the wettest January-June on record for Illinois with 28.96 inches (9.13 inches above average).

This is the third month in a row with below-average precipitation. In July, Illinois received 3.14 inches (0.91 inches below average). In August, Illinois received 1.63 inches (1.37 inches below average).


The statewide temperature for Illinois in September was 68.8 degrees, 2.9 degrees above average. It was warm but not record-setting. The warmest September on record was 1925 with 72.7 degrees.

The above-average September reversed the pattern of the last three months (June, July, and August) which were below-average on temperature.

  • June: 71.4° (0.4° below average)
  • July: 72.9° (2.4° below average)
  • August: 72.5° (1.0° below average)
  • September: 68.8° (2.9° above average)

Statewide records began in 1895.