September weather in Williamsport, PA
The average temperature in Williamsport in September is 65.5°F (54.7°F–76.3°F). Average precipitation: 4.54 inches.
September is a fall month in Williamsport, and is warmer than the annual average of 51.8°F. Daily temperatures swing about 21.6°F between overnight low and afternoon high. Expect about 11 days with precipitation. Daylight averages about 12h 16m. For travel, September is a comfortable month to visit.
Avg High
76.3°F
Avg Low
54.7°F
Precipitation
4.54 in
Daylight
12h 16m
September records in Williamsport
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 93.0°F (2010) | 46.0°F (2009) | 1.83 in (2021) |
| September 2 | 93.9°F (2010) | 44.1°F (2017) | 4.35 in (2006) |
| September 3 | 93.0°F (2018) | 46.0°F (2001) | 0.46 in (2017) |
| September 4 | 93.9°F (2008) | 48.0°F (2024) | 1.75 in (2011) |
| September 5 | 91.9°F (2008) | 45.0°F (2010) | 1.19 in (2022) |
| September 6 | 93.0°F (2018) | 42.1°F (2000) | 0.85 in (2011) |
| September 7 | 93.9°F (2016) | 44.1°F (2000) | 5.56 in (1999) |
| September 8 | 93.9°F (2015) | 44.1°F (2025) | 1.89 in (2011) |
| September 9 | 98.1°F (2002) | 43.0°F (2024) | 1.57 in (2008) |
| September 10 | 99.0°F (2002) | 46.9°F (2017) | 2.41 in (2018) |
| September 11 | 93.0°F (2013) | 46.0°F (2005) | 1.76 in (1997) |
| September 12 | 90.0°F (2005) | 48.0°F (2002) | 1.25 in (2000) |
| September 13 | 90.0°F (2005) | 45.0°F (2002) | 0.71 in (2001) |
| September 14 | 90.0°F (2002) | 46.9°F (2013) | 0.44 in (2001) |
| September 15 | 89.1°F (2005) | 43.0°F (2020) | 0.53 in (2021) |
| September 16 | 87.1°F (2005) | 39.9°F (2007) | 2.21 in (1999) |
| September 17 | 84.0°F (2002) | 39.0°F (2013) | 3.83 in (2004) |
| September 18 | 88.0°F (2025) | 41.0°F (2000) | 2.47 in (2004) |
| September 19 | 87.1°F (2025) | 36.0°F (2020) | 1.15 in (2003) |
| September 20 | 88.0°F (2016) | 37.9°F (2020) | 0.48 in (2001) |
| September 21 | 86.0°F (2005) | 35.1°F (2020) | 0.51 in (2014) |
| September 22 | 89.1°F (2007) | 35.1°F (2020) | 1.48 in (2002) |
| September 23 | 90.0°F (2016) | 43.0°F (1999) | 2.66 in (2021) |
| September 24 | 93.0°F (2017) | 42.1°F (2013) | 1.89 in (2001) |
| September 25 | 91.9°F (2017) | 44.1°F (2000) | 1.06 in (2025) |
| September 26 | 91.0°F (2017) | 41.0°F (2001) | 0.51 in (2018) |
| September 27 | 91.0°F (2017) | 43.0°F (2000) | 1.52 in (2008) |
| September 28 | 86.0°F (2025) | 39.0°F (2000) | 2.36 in (2004) |
| September 29 | 79.0°F (2014) | 33.1°F (2000) | 1.61 in (1997) |
| September 30 | 82.9°F (2025) | 34.0°F (2000) | 3.50 in (2010) |