September weather in Waterloo, IA
The average temperature in Waterloo in September is 64.6°F (52.4°F–76.8°F). Average precipitation: 3.14 inches.
September is a fall month in Waterloo, and is warmer than the annual average of 49°F. Daily temperatures swing about 24.4°F between overnight low and afternoon high. Expect about 9 days with precipitation. Daylight averages about 12h 16m. For travel, September is one of the best months of the year to visit.
Avg High
76.8°F
Avg Low
52.4°F
Precipitation
3.14 in
Daylight
12h 16m
September records in Waterloo
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 97.0°F (1984) | 36.0°F (1967) | 3.23 in (2018) |
| September 2 | 98.1°F (2023) | 37.9°F (1967) | 1.28 in (2018) |
| September 3 | 100.0°F (2023) | 36.0°F (1974) | 2.57 in (2018) |
| September 4 | 100.0°F (2023) | 34.0°F (1974) | 1.40 in (1956) |
| September 5 | 93.0°F (1960) | 37.0°F (1974) | 2.52 in (1958) |
| September 6 | 93.9°F (1960) | 35.1°F (1988) | 1.49 in (1965) |
| September 7 | 95.0°F (1978) | 37.0°F (1956) | 1.95 in (2001) |
| September 8 | 95.0°F (1978) | 35.1°F (1986) | 2.65 in (1964) |
| September 9 | 99.0°F (2013) | 37.0°F (1969) | 1.56 in (2019) |
| September 10 | 97.0°F (2013) | 35.1°F (1976) | 1.75 in (2006) |
| September 11 | 98.1°F (2000) | 34.0°F (1955) | 2.35 in (2006) |
| September 12 | 93.9°F (1998) | 32.0°F (1955) | 3.05 in (1978) |
| September 13 | 95.0°F (2025) | 30.9°F (1975) | 1.60 in (1978) |
| September 14 | 93.9°F (1994) | 34.0°F (1996) | 0.86 in (1970) |
| September 15 | 95.0°F (1955) | 30.0°F (2007) | 1.51 in (2016) |
| September 16 | 91.9°F (1955) | 30.9°F (1984) | 0.82 in (1978) |
| September 17 | 95.0°F (1988) | 35.1°F (1980) | 2.12 in (1977) |
| September 18 | 93.0°F (1955) | 35.1°F (1973) | 1.34 in (2018) |
| September 19 | 91.0°F (1984) | 32.0°F (1991) | 1.78 in (2018) |
| September 20 | 96.1°F (2022) | 27.0°F (1991) | 1.67 in (1965) |
| September 21 | 93.0°F (2024) | 30.9°F (1974) | 3.08 in (1950) |
| September 22 | 93.0°F (2017) | 26.1°F (1974) | 3.21 in (2016) |
| September 23 | 91.9°F (2017) | 28.0°F (1983) | 0.92 in (1977) |
| September 24 | 91.0°F (1984) | 28.9°F (1989) | 1.15 in (1986) |
| September 25 | 89.1°F (2017) | 30.9°F (1975) | 1.21 in (1981) |
| September 26 | 89.1°F (2025) | 26.1°F (1984) | 1.92 in (1959) |
| September 27 | 89.1°F (1954) | 32.0°F (1975) | 1.53 in (1965) |
| September 28 | 91.0°F (1953) | 28.0°F (1967) | 1.34 in (1974) |
| September 29 | 90.0°F (1953) | 21.9°F (1967) | 1.94 in (1973) |
| September 30 | 93.9°F (2023) | 27.0°F (1984) | 1.69 in (2007) |