September weather in Alton, MO
The average temperature in Alton in September is 68.1°F (55.4°F–80.8°F). Average precipitation: 3.46 inches.
September is a fall month in Alton, and is warmer than the annual average of 55.7°F. Daily temperatures swing about 25.4°F between overnight low and afternoon high. Expect about 5 days with precipitation. Daylight averages about 12h 13m. For travel, September is a comfortable month to visit.
Avg High
80.8°F
Avg Low
55.4°F
Precipitation
3.46 in
Daylight
12h 13m
September records in Alton
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 100.9°F (2000) | 48.9°F (1976) | 1.97 in (2012) |
| September 2 | 100.0°F (1980) | 45.0°F (1965) | 2.73 in (1957) |
| September 3 | 100.0°F (2000) | 46.0°F (1965) | 1.08 in (2008) |
| September 4 | 102.9°F (2000) | 41.0°F (1974) | 3.10 in (2008) |
| September 5 | 100.0°F (1999) | 43.0°F (1997) | 1.76 in (2009) |
| September 6 | 98.1°F (1983) | 44.1°F (1997) | 1.25 in (1946) |
| September 7 | 100.0°F (1980) | 42.1°F (2011) | 1.70 in (1946) |
| September 8 | 98.1°F (1980) | 42.1°F (2011) | 1.72 in (1967) |
| September 9 | 100.0°F (1980) | 42.1°F (2025) | 2.24 in (1967) |
| September 10 | 100.0°F (1980) | 39.9°F (1969) | 1.10 in (1950) |
| September 11 | 96.1°F (2013) | 37.0°F (1976) | 4.50 in (1975) |
| September 12 | 96.1°F (2000) | 39.0°F (1976) | 2.22 in (1975) |
| September 13 | 99.0°F (1980) | 42.1°F (1975) | 2.20 in (1951) |
| September 14 | 100.0°F (1980) | 37.9°F (1979) | 2.60 in (1945) |
| September 15 | 97.0°F (2000) | 36.0°F (1979) | 2.51 in (1962) |
| September 16 | 93.9°F (2025) | 36.0°F (1979) | 3.82 in (1996) |
| September 17 | 100.0°F (1980) | 34.0°F (1981) | 1.68 in (1968) |
| September 18 | 93.9°F (1972) | 34.0°F (1981) | 1.48 in (1964) |
| September 19 | 93.0°F (2025) | 36.0°F (1981) | 1.50 in (1975) |
| September 20 | 95.0°F (2000) | 36.0°F (1981) | 1.27 in (1971) |
| September 21 | 95.0°F (2000) | 37.0°F (1983) | 0.94 in (2013) |
| September 22 | 91.9°F (1980) | 32.0°F (1983) | 3.70 in (1965) |
| September 23 | 91.0°F (2005) | 32.0°F (1995) | 4.77 in (2006) |
| September 24 | 90.0°F (2007) | 32.0°F (1983) | 1.30 in (1997) |
| September 25 | 90.0°F (1999) | 33.1°F (1995) | 2.47 in (1945) |
| September 26 | 93.0°F (1998) | 33.1°F (1995) | 1.86 in (1966) |
| September 27 | 91.0°F (1981) | 36.0°F (2001) | 2.53 in (1996) |
| September 28 | 93.9°F (1998) | 37.9°F (1967) | 1.51 in (1945) |
| September 29 | 93.0°F (1998) | 30.9°F (1967) | 1.13 in (1974) |
| September 30 | 96.1°F (1998) | 34.0°F (2003) | 0.98 in (1966) |