September weather in Roslyn, WA
The average temperature in Roslyn in September is 56.2°F (43.3°F–69.0°F). Average precipitation: 1.88 inches.
September is a fall month in Roslyn, and is warmer than the annual average of 45.2°F. Daily temperatures swing about 25.7°F between overnight low and afternoon high. Daylight averages about 12h 19m. For travel, September is a comfortable month to visit.
Avg High
69.0°F
Avg Low
43.3°F
Precipitation
1.88 in
Daylight
12h 19m
September records in Roslyn
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 93.0°F (2022) | 35.1°F (2006) | 1.05 in (2010) |
| September 2 | 93.9°F (2024) | 34.0°F (2006) | 0.54 in (2004) |
| September 3 | 96.1°F (2025) | 33.1°F (2006) | 0.45 in (2014) |
| September 4 | 97.0°F (2025) | 37.0°F (2002) | 0.10 in (2009) |
| September 5 | 91.9°F (2020) | 35.1°F (2002) | 0.22 in (2009) |
| September 6 | 90.0°F (2024) | 34.0°F (2002) | 1.38 in (2013) |
| September 7 | 93.0°F (2024) | 37.9°F (2002) | 1.13 in (2009) |
| September 8 | 89.1°F (2011) | 37.0°F (2007) | 1.03 in (2010) |
| September 9 | 84.0°F (2012) | 37.9°F (2007) | 0.16 in (2010) |
| September 10 | 89.1°F (2011) | 34.0°F (2006) | 0.27 in (2005) |
| September 11 | 91.9°F (2011) | 35.1°F (2006) | 0.78 in (2004) |
| September 12 | 93.0°F (2011) | 30.9°F (2012) | 0.30 in (2003) |
| September 13 | 89.1°F (2013) | 33.1°F (2012) | 0.07 in (2004) |
| September 14 | 86.0°F (2002) | 34.0°F (2003) | 6.00 in (1905) |
| September 15 | 82.0°F (2002) | 36.0°F (2008) | 0.34 in (2004) |
| September 16 | 84.0°F (2023) | 37.9°F (2008) | 0.47 in (2006) |
| September 17 | 88.0°F (2008) | 36.0°F (2018) | 0.33 in (2003) |
| September 18 | 82.9°F (2025) | 36.0°F (2018) | 0.47 in (2016) |
| September 19 | 84.9°F (2012) | 36.0°F (1933) | 0.38 in (2021) |
| September 20 | 86.0°F (2012) | 37.0°F (2013) | 0.33 in (2021) |
| September 21 | 82.9°F (2012) | 34.0°F (2005) | 0.26 in (2006) |
| September 22 | 79.0°F (2014) | 34.0°F (1933) | 0.28 in (1933) |
| September 23 | 80.1°F (2009) | 32.0°F (2002) | 0.46 in (2013) |
| September 24 | 86.0°F (2009) | 34.0°F (1933) | 0.97 in (2020) |
| September 25 | 84.0°F (2024) | 28.9°F (1933) | 0.40 in (2020) |
| September 26 | 80.1°F (2003) | 30.9°F (2004) | 0.90 in (1950) |
| September 27 | 84.0°F (2003) | 27.0°F (2004) | 2.00 in (1905) |
| September 28 | 87.1°F (2022) | 28.9°F (2005) | 0.96 in (2013) |
| September 29 | 86.0°F (2003) | 33.1°F (2004) | 1.40 in (1906) |
| September 30 | 84.9°F (2003) | 30.0°F (1933) | 2.00 in (2005) |