September weather in Interior, SD
The average temperature in Interior in September is 66.2°F (50.5°F–81.8°F). Average precipitation: 1.39 inches.
September is a fall month in Interior, and is warmer than the annual average of 50.4°F. Daily temperatures swing about 31.3°F between overnight low and afternoon high. Expect about 6 days with precipitation. Daylight averages about 12h 17m. For travel, September is a comfortable month to visit.
Avg High
81.8°F
Avg Low
50.5°F
Precipitation
1.39 in
Daylight
12h 17m
September records in Interior
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 105.1°F (1983) | 39.0°F (1981) | 1.84 in (2025) |
| September 2 | 105.1°F (1971) | 39.9°F (1974) | 0.99 in (2021) |
| September 3 | 102.9°F (1960) | 37.0°F (1974) | 1.52 in (1999) |
| September 4 | 106.0°F (2001) | 39.9°F (1962) | 0.91 in (1999) |
| September 5 | 105.1°F (2020) | 37.9°F (1968) | 2.24 in (2004) |
| September 6 | 104.0°F (2002) | 32.0°F (1956) | 0.56 in (1996) |
| September 7 | 102.0°F (1983) | 35.1°F (1986) | 1.03 in (1970) |
| September 8 | 105.1°F (1959) | 36.0°F (2020) | 0.98 in (1985) |
| September 9 | 105.1°F (1979) | 34.0°F (2020) | 1.76 in (2002) |
| September 10 | 102.0°F (1982) | 32.0°F (2020) | 0.73 in (1989) |
| September 11 | 102.0°F (1966) | 32.0°F (1989) | 0.41 in (1985) |
| September 12 | 100.0°F (1990) | 30.9°F (2014) | 0.65 in (1961) |
| September 13 | 100.0°F (1990) | 33.1°F (1970) | 1.24 in (1966) |
| September 14 | 97.0°F (1955) | 28.0°F (1993) | 0.79 in (2024) |
| September 15 | 102.9°F (1955) | 33.1°F (1961) | 0.56 in (2017) |
| September 16 | 98.1°F (1979) | 32.0°F (1965) | 0.80 in (1977) |
| September 17 | 102.9°F (2000) | 33.1°F (1965) | 0.54 in (1959) |
| September 18 | 100.9°F (2000) | 28.9°F (1991) | 1.29 in (1996) |
| September 19 | 100.0°F (2021) | 27.0°F (1991) | 1.61 in (1993) |
| September 20 | 98.1°F (2022) | 25.0°F (1964) | 3.31 in (1955) |
| September 21 | 93.0°F (2007) | 28.9°F (1995) | 2.02 in (1989) |
| September 22 | 96.1°F (2013) | 28.0°F (1995) | 1.62 in (2006) |
| September 23 | 99.0°F (1958) | 32.0°F (1990) | 2.54 in (2008) |
| September 24 | 96.1°F (1992) | 27.0°F (1985) | 0.38 in (2017) |
| September 25 | 95.0°F (1964) | 36.0°F (2003) | 0.71 in (1996) |
| September 26 | 102.0°F (2024) | 25.0°F (1972) | 0.09 in (1973) |
| September 27 | 100.0°F (2024) | 28.9°F (1967) | 0.10 in (2006) |
| September 28 | 99.0°F (2024) | 26.1°F (1976) | 0.32 in (2015) |
| September 29 | 100.0°F (2024) | 30.9°F (1985) | 0.83 in (1965) |
| September 30 | 100.0°F (2024) | 27.0°F (1974) | 0.75 in (2014) |