September weather in St. Marys, IA
The average temperature in St. Marys in September is 65.0°F (52.4°F–77.6°F). Average precipitation: 3.86 inches.
September is a fall month in St. Marys, and is warmer than the annual average of 49.9°F. Daily temperatures swing about 25.2°F between overnight low and afternoon high. Expect about 8 days with precipitation. Daylight averages about 12h 16m. For travel, September is one of the best months of the year to visit.
Avg High
77.6°F
Avg Low
52.4°F
Precipitation
3.86 in
Daylight
12h 16m
September records in St. Marys
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 99.0°F (1953) | 36.0°F (1967) | 1.70 in (1935) |
| September 2 | 98.1°F (1897) | 43.0°F (1893) | 6.80 in (1909) |
| September 3 | 102.9°F (1939) | 43.0°F (1952) | 3.68 in (1941) |
| September 4 | 100.0°F (1925) | 35.1°F (1974) | 1.07 in (1956) |
| September 5 | 99.0°F (1899) | 26.1°F (1984) | 1.85 in (1902) |
| September 6 | 100.9°F (1939) | 39.9°F (1988) | 1.86 in (1911) |
| September 7 | 102.0°F (1939) | 37.9°F (1956) | 1.40 in (1981) |
| September 8 | 104.0°F (1947) | 17.1°F (1984) | 2.82 in (2001) |
| September 9 | 100.9°F (1933) | 37.9°F (2008) | 2.10 in (1989) |
| September 10 | 100.9°F (1927) | 35.1°F (1976) | 4.68 in (2014) |
| September 11 | 100.0°F (1927) | 37.0°F (1940) | 1.87 in (1972) |
| September 12 | 98.1°F (1927) | 35.1°F (1940) | 3.40 in (1961) |
| September 13 | 98.1°F (1939) | 35.1°F (2014) | 3.02 in (2008) |
| September 14 | 99.0°F (1939) | 34.0°F (1923) | 4.11 in (1914) |
| September 15 | 99.0°F (1927) | 30.0°F (1979) | 2.71 in (1992) |
| September 16 | 96.1°F (1895) | 33.1°F (2007) | 2.01 in (1941) |
| September 17 | 95.0°F (1925) | 33.1°F (1943) | 1.23 in (1977) |
| September 18 | 96.1°F (1947) | 30.0°F (1981) | 1.96 in (1978) |
| September 19 | 99.0°F (1948) | 30.9°F (1991) | 11.21 in (1931) |
| September 20 | 91.9°F (1931) | 30.0°F (1991) | 3.31 in (1978) |
| September 21 | 96.1°F (1937) | 32.0°F (1918) | 2.55 in (1919) |
| September 22 | 99.0°F (1937) | 28.0°F (1979) | 1.40 in (2019) |
| September 23 | 93.0°F (2017) | 28.0°F (1995) | 2.98 in (1935) |
| September 24 | 96.1°F (1984) | 28.9°F (2012) | 2.45 in (1960) |
| September 25 | 91.9°F (2017) | 30.9°F (1942) | 2.36 in (1901) |
| September 26 | 93.9°F (1956) | 27.0°F (1984) | 2.27 in (1936) |
| September 27 | 93.9°F (1956) | 28.9°F (1942) | 1.64 in (1924) |
| September 28 | 100.9°F (1953) | 23.0°F (1942) | 2.24 in (1911) |
| September 29 | 91.0°F (1953) | 23.0°F (1899) | 2.20 in (1955) |
| September 30 | 93.0°F (1952) | 28.0°F (1895) | 1.83 in (1902) |