September weather in Sullivan, WI
The average temperature in Sullivan in September is 62.0°F (50.8°F–73.3°F). Average precipitation: 3.47 inches.
September is a fall month in Sullivan, and is warmer than the annual average of 46.6°F. Daily temperatures swing about 22.5°F between overnight low and afternoon high. Expect about 9 days with precipitation. Daylight averages about 12h 17m. For travel, September is one of the best months of the year to visit.
Avg High
73.3°F
Avg Low
50.8°F
Precipitation
3.47 in
Daylight
12h 17m
September records in Sullivan
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 91.9°F (2000) | 43.0°F (2001) | 0.45 in (2010) |
| September 2 | 93.0°F (2000) | 42.1°F (2017) | 1.14 in (2018) |
| September 3 | 93.0°F (2008) | 46.0°F (2009) | 0.74 in (2018) |
| September 4 | 91.9°F (2023) | 36.0°F (2025) | 0.50 in (2001) |
| September 5 | 91.0°F (1996) | 37.9°F (2025) | 2.42 in (2018) |
| September 6 | 91.9°F (1999) | 41.0°F (2025) | 0.37 in (2020) |
| September 7 | 93.0°F (1998) | 36.0°F (2025) | 1.72 in (2016) |
| September 8 | 90.0°F (2005) | 36.0°F (2025) | 1.27 in (2001) |
| September 9 | 91.0°F (2002) | 39.0°F (2008) | 0.25 in (2008) |
| September 10 | 95.0°F (2013) | 43.0°F (1995) | 1.21 in (2001) |
| September 11 | 91.0°F (2005) | 41.0°F (2014) | 3.47 in (2022) |
| September 12 | 91.9°F (2005) | 37.9°F (2014) | 2.95 in (2000) |
| September 13 | 95.0°F (1998) | 37.0°F (2014) | 2.05 in (2025) |
| September 14 | 96.1°F (1998) | 39.0°F (2013) | 1.32 in (2003) |
| September 15 | 87.1°F (2024) | 28.9°F (2007) | 1.18 in (1998) |
| September 16 | 88.0°F (2017) | 30.0°F (2007) | 0.09 in (2004) |
| September 17 | 88.0°F (2018) | 39.0°F (2000) | 2.03 in (2015) |
| September 18 | 82.9°F (2024) | 39.9°F (2020) | 0.91 in (2015) |
| September 19 | 88.0°F (2021) | 36.0°F (2020) | 0.90 in (2001) |
| September 20 | 91.0°F (2017) | 37.9°F (2006) | 0.92 in (2018) |
| September 21 | 88.0°F (2017) | 37.0°F (1999) | 0.93 in (2016) |
| September 22 | 93.9°F (2017) | 34.0°F (1995) | 3.05 in (2024) |
| September 23 | 93.9°F (2017) | 32.0°F (1995) | 1.36 in (2000) |
| September 24 | 90.0°F (2017) | 33.1°F (2002) | 1.26 in (2001) |
| September 25 | 91.9°F (2017) | 34.0°F (2001) | 0.60 in (2016) |
| September 26 | 89.1°F (2017) | 34.0°F (2001) | 1.65 in (2023) |
| September 27 | 93.0°F (1998) | 36.0°F (2010) | 1.22 in (1996) |
| September 28 | 82.9°F (2025) | 37.0°F (2022) | 1.51 in (1999) |
| September 29 | 84.0°F (2014) | 33.1°F (2018) | 1.37 in (2019) |
| September 30 | 86.0°F (2025) | 34.0°F (2003) | 0.76 in (2018) |