September weather in Decatur, IL
The average temperature in Decatur in September is 67.3°F (57.0°F–77.7°F). Average precipitation: 3.08 inches.
September is a fall month in Decatur, and is warmer than the annual average of 53°F. Daily temperatures swing about 20.7°F between overnight low and afternoon high. Expect about 8 days with precipitation. Daylight averages about 12h 15m. For travel, September is one of the best months of the year to visit.
Avg High
77.7°F
Avg Low
57.0°F
Precipitation
3.08 in
Daylight
12h 15m
September records in Decatur
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 102.0°F (1953) | 41.0°F (1987) | 2.72 in (2003) |
| September 2 | 102.0°F (1913) | 45.0°F (1901) | 2.60 in (2010) |
| September 3 | 102.0°F (1913) | 43.0°F (1952) | 2.31 in (2022) |
| September 4 | 102.9°F (1913) | 41.0°F (1928) | 4.20 in (1926) |
| September 5 | 104.0°F (1954) | 45.0°F (1902) | 1.60 in (1921) |
| September 6 | 102.9°F (1925) | 37.0°F (1988) | 3.22 in (1971) |
| September 7 | 102.0°F (1899) | 39.9°F (1988) | 2.22 in (2018) |
| September 8 | 100.0°F (1922) | 34.0°F (1986) | 2.42 in (1927) |
| September 9 | 100.9°F (1933) | 39.0°F (1986) | 3.60 in (1926) |
| September 10 | 99.0°F (1919) | 39.9°F (1924) | 1.70 in (1905) |
| September 11 | 99.0°F (1897) | 35.1°F (1917) | 1.04 in (1944) |
| September 12 | 99.0°F (1897) | 37.9°F (1955) | 1.70 in (1949) |
| September 13 | 100.0°F (1939) | 35.1°F (1902) | 2.38 in (1911) |
| September 14 | 100.9°F (1939) | 34.0°F (1923) | 5.84 in (2008) |
| September 15 | 100.9°F (1939) | 37.9°F (1979) | 2.05 in (1931) |
| September 16 | 99.0°F (1939) | 32.0°F (1916) | 2.20 in (1965) |
| September 17 | 97.0°F (1927) | 35.1°F (1937) | 4.11 in (1969) |
| September 18 | 96.1°F (1983) | 32.0°F (1901) | 4.66 in (1904) |
| September 19 | 97.0°F (1955) | 32.0°F (1901) | 2.46 in (1966) |
| September 20 | 96.1°F (1940) | 30.9°F (1991) | 2.65 in (1986) |
| September 21 | 95.0°F (1955) | 30.9°F (1897) | 2.41 in (1947) |
| September 22 | 93.9°F (1930) | 30.0°F (1983) | 1.79 in (1965) |
| September 23 | 91.9°F (1905) | 28.9°F (1983) | 1.78 in (1959) |
| September 24 | 93.0°F (1933) | 30.9°F (1928) | 1.43 in (1961) |
| September 25 | 91.0°F (1897) | 1.0°F (1986) | 2.18 in (1926) |
| September 26 | 96.1°F (1897) | 27.0°F (1928) | 3.00 in (1904) |
| September 27 | 93.0°F (1954) | 30.9°F (1899) | 1.82 in (1936) |
| September 28 | 96.1°F (1953) | 28.0°F (1942) | 1.64 in (1936) |
| September 29 | 100.0°F (1953) | 28.0°F (1899) | 3.63 in (1955) |
| September 30 | 93.9°F (1922) | 19.9°F (1899) | 2.31 in (1927) |