September weather in Mount Vernon, IL
The average temperature in Mount Vernon in September is 67.7°F (56.7°F–78.6°F). Average precipitation: 3.37 inches.
September is a fall month in Mount Vernon, and is warmer than the annual average of 54.5°F. Daily temperatures swing about 21.9°F between overnight low and afternoon high. Expect about 8 days with precipitation. Daylight averages about 12h 14m. For travel, September is one of the best months of the year to visit.
Avg High
78.6°F
Avg Low
56.7°F
Precipitation
3.37 in
Daylight
12h 14m
September records in Mount Vernon
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 102.0°F (1943) | 44.1°F (1949) | 1.85 in (1952) |
| September 2 | 102.9°F (1913) | 42.1°F (1949) | 4.25 in (1931) |
| September 3 | 102.9°F (1913) | 46.0°F (1952) | 2.76 in (1932) |
| September 4 | 102.9°F (1913) | 43.0°F (1928) | 2.62 in (1991) |
| September 5 | 104.0°F (1899) | 42.1°F (1902) | 2.45 in (1910) |
| September 6 | 104.0°F (1899) | 41.0°F (1988) | 2.15 in (1910) |
| September 7 | 102.9°F (1899) | 39.9°F (1898) | 0.90 in (1969) |
| September 8 | 104.0°F (1939) | 39.9°F (1898) | 3.17 in (1990) |
| September 9 | 102.0°F (1939) | 42.1°F (1949) | 2.50 in (1976) |
| September 10 | 100.0°F (1919) | 39.9°F (1902) | 1.34 in (1951) |
| September 11 | 99.0°F (1897) | 39.9°F (1917) | 2.15 in (1984) |
| September 12 | 102.0°F (1936) | 39.0°F (1940) | 2.15 in (1988) |
| September 13 | 102.0°F (1936) | 36.0°F (1902) | 2.80 in (1943) |
| September 14 | 102.9°F (1939) | 35.1°F (1902) | 1.18 in (1981) |
| September 15 | 105.1°F (1939) | 32.0°F (1902) | 2.35 in (1930) |
| September 16 | 99.0°F (1927) | 37.9°F (1916) | 2.97 in (1930) |
| September 17 | 99.0°F (1927) | 39.9°F (1900) | 3.10 in (1905) |
| September 18 | 97.0°F (1953) | 37.9°F (1937) | 2.25 in (1896) |
| September 19 | 99.0°F (1940) | 35.1°F (1901) | 1.95 in (1966) |
| September 20 | 99.0°F (1940) | 37.9°F (1991) | 2.68 in (1954) |
| September 21 | 100.0°F (1940) | 34.0°F (1927) | 1.58 in (1954) |
| September 22 | 98.1°F (1940) | 32.0°F (1983) | 1.92 in (1909) |
| September 23 | 95.0°F (1980) | 28.9°F (1983) | 3.15 in (1984) |
| September 24 | 93.9°F (1935) | 28.0°F (1928) | 1.92 in (1951) |
| September 25 | 93.0°F (1920) | 35.1°F (1950) | 2.60 in (2018) |
| September 26 | 95.0°F (1897) | 28.9°F (1928) | 2.59 in (1911) |
| September 27 | 91.9°F (1946) | 33.1°F (1899) | 3.26 in (1945) |
| September 28 | 96.1°F (1953) | 32.0°F (1942) | 1.42 in (1927) |
| September 29 | 100.0°F (1953) | 33.1°F (1899) | 1.59 in (1974) |
| September 30 | 93.9°F (1971) | 23.0°F (1899) | 1.98 in (1929) |