September weather in Stonington, IL
The average temperature in Stonington in September is °F (°F–°F). Average precipitation: 3.72 inches.
September is a fall month in Stonington, and is cooler than the annual average of 0°F. Expect about 6 days with precipitation. Daylight averages about 12h 15m.
Avg High
°F
Avg Low
°F
Precipitation
3.72 in
Daylight
12h 15m
September records in Stonington
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 84.9°F (2021) | 52.0°F (2023) | 4.90 in (2012) |
| September 2 | 82.9°F (2024) | 51.1°F (2025) | 1.39 in (1941) |
| September 3 | 88.0°F (2023) | 51.1°F (2025) | 2.40 in (2010) |
| September 4 | 89.1°F (2023) | 50.0°F (2020) | 0.87 in (1953) |
| September 5 | 91.0°F (2023) | 51.1°F (2025) | 2.16 in (2008) |
| September 6 | 88.0°F (2024) | 46.0°F (2025) | 3.70 in (2009) |
| September 7 | 87.1°F (2020) | 42.1°F (2025) | 0.32 in (2007) |
| September 8 | 87.1°F (2020) | 39.9°F (2024) | 1.04 in (1970) |
| September 9 | 87.1°F (2020) | 39.9°F (2024) | 3.16 in (2007) |
| September 10 | 82.9°F (2020) | 45.0°F (2024) | 0.63 in (2014) |
| September 11 | 88.0°F (2025) | 50.0°F (2024) | 1.80 in (2014) |
| September 12 | 90.0°F (2025) | 52.0°F (2022) | 1.87 in (2008) |
| September 13 | 91.0°F (2025) | 52.0°F (2022) | 1.95 in (1945) |
| September 14 | 96.1°F (2025) | 48.0°F (2023) | 2.35 in (2008) |
| September 15 | 99.0°F (2025) | 45.0°F (2023) | 2.40 in (2008) |
| September 16 | 91.9°F (2025) | 51.1°F (2023) | 1.34 in (2014) |
| September 17 | 91.0°F (2025) | 52.0°F (2023) | 4.32 in (1969) |
| September 18 | 95.0°F (2025) | 46.9°F (2023) | 1.95 in (2002) |
| September 19 | 93.9°F (2025) | 39.0°F (2020) | 2.37 in (2022) |
| September 20 | 91.0°F (2024) | 39.9°F (2020) | 1.37 in (1954) |
| September 21 | 95.0°F (2022) | 43.0°F (2020) | 1.96 in (1947) |
| September 22 | 91.9°F (2022) | 48.0°F (2020) | 1.78 in (2025) |
| September 23 | 84.0°F (2023) | 45.0°F (2021) | 1.48 in (1972) |
| September 24 | 86.0°F (2023) | 45.0°F (2021) | 2.20 in (2024) |
| September 25 | 86.0°F (2023) | 46.0°F (2021) | 2.61 in (1961) |
| September 26 | 86.0°F (2023) | 48.0°F (2021) | 0.87 in (2003) |
| September 27 | 88.0°F (2023) | 37.9°F (2022) | 1.74 in (1972) |
| September 28 | 90.0°F (2021) | 37.0°F (2022) | 0.95 in (1944) |
| September 29 | 90.0°F (2025) | 39.0°F (2022) | 0.62 in (2019) |
| September 30 | 90.0°F (2025) | 39.0°F (2022) | 1.36 in (1955) |