September weather in Monmouth, IL
The average temperature in Monmouth in September is 65.4°F (53.6°F–77.3°F). Average precipitation: 3.70 inches.
September is a fall month in Monmouth, and is warmer than the annual average of 50.6°F. Daily temperatures swing about 23.7°F between overnight low and afternoon high. Expect about 7 days with precipitation. Daylight averages about 12h 15m. For travel, September is one of the best months of the year to visit.
Avg High
77.3°F
Avg Low
53.6°F
Precipitation
3.70 in
Daylight
12h 15m
September records in Monmouth
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 102.0°F (1913) | 39.9°F (1967) | 3.42 in (1931) |
| September 2 | 102.0°F (1913) | 41.0°F (1946) | 2.05 in (2012) |
| September 3 | 102.9°F (1913) | 42.1°F (1952) | 1.45 in (1926) |
| September 4 | 100.0°F (1925) | 39.0°F (1974) | 2.55 in (2008) |
| September 5 | 102.0°F (1899) | 39.9°F (1962) | 1.89 in (1898) |
| September 6 | 102.0°F (1899) | 39.9°F (1962) | 2.43 in (1898) |
| September 7 | 100.0°F (1899) | 39.0°F (1956) | 2.45 in (2018) |
| September 8 | 98.1°F (1912) | 41.0°F (2024) | 2.33 in (1948) |
| September 9 | 98.1°F (1897) | 41.0°F (1924) | 2.90 in (1992) |
| September 10 | 98.1°F (1897) | 41.0°F (1967) | 3.52 in (2014) |
| September 11 | 96.1°F (1906) | 34.0°F (1917) | 2.01 in (1896) |
| September 12 | 98.1°F (1897) | 36.0°F (1902) | 2.10 in (1928) |
| September 13 | 99.0°F (1897) | 30.9°F (1902) | 4.04 in (1961) |
| September 14 | 99.0°F (1939) | 33.1°F (1923) | 3.14 in (1894) |
| September 15 | 99.0°F (1939) | 34.0°F (2007) | 2.60 in (2004) |
| September 16 | 96.1°F (1906) | 33.1°F (1916) | 1.78 in (1897) |
| September 17 | 98.1°F (1927) | 36.0°F (1900) | 1.58 in (2023) |
| September 18 | 95.0°F (1906) | 33.1°F (1916) | 1.10 in (1915) |
| September 19 | 93.0°F (1908) | 32.0°F (1901) | 4.18 in (1906) |
| September 20 | 93.0°F (1908) | 28.9°F (1896) | 1.33 in (1950) |
| September 21 | 95.0°F (2018) | 33.1°F (1901) | 4.45 in (1947) |
| September 22 | 91.9°F (1930) | 30.0°F (1995) | 2.95 in (1970) |
| September 23 | 91.9°F (2017) | 28.9°F (1995) | 1.94 in (1961) |
| September 24 | 93.0°F (2017) | 32.0°F (1942) | 4.48 in (1911) |
| September 25 | 91.9°F (1920) | 32.0°F (1942) | 1.79 in (1895) |
| September 26 | 93.0°F (1897) | 30.0°F (1926) | 2.00 in (1933) |
| September 27 | 91.0°F (1990) | 33.1°F (1899) | 1.55 in (1911) |
| September 28 | 95.0°F (1953) | 26.1°F (1942) | 3.75 in (2019) |
| September 29 | 100.0°F (1953) | 27.0°F (1899) | 2.21 in (1986) |
| September 30 | 91.0°F (1952) | 18.0°F (1899) | 1.12 in (1925) |