September weather in Cosmopolis, WA
The average temperature in Cosmopolis in September is 59.9°F (51.1°F–68.7°F). Average precipitation: 2.73 inches.
September is a fall month in Cosmopolis, and is warmer than the annual average of 51.3°F. Daily temperatures swing about 17.6°F between overnight low and afternoon high. Expect about 9 days with precipitation. Daylight averages about 12h 19m. For travel, September is one of the best months of the year to visit.
Avg High
68.7°F
Avg Low
51.1°F
Precipitation
2.73 in
Daylight
12h 19m
September records in Cosmopolis
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 91.9°F (1905) | 39.0°F (1906) | 1.31 in (2010) |
| September 2 | 93.0°F (1934) | 39.9°F (1902) | 2.16 in (1971) |
| September 3 | 100.0°F (1988) | 39.9°F (1907) | 2.10 in (1913) |
| September 4 | 91.9°F (1909) | 37.9°F (1912) | 1.96 in (1945) |
| September 5 | 97.0°F (1944) | 39.9°F (1947) | 1.92 in (1931) |
| September 6 | 91.9°F (1955) | 34.0°F (1911) | 1.58 in (1906) |
| September 7 | 93.0°F (1907) | 34.0°F (1911) | 2.10 in (1906) |
| September 8 | 93.0°F (1958) | 39.0°F (1922) | 0.94 in (1992) |
| September 9 | 91.0°F (1948) | 37.9°F (1924) | 1.45 in (1978) |
| September 10 | 91.9°F (2020) | 37.0°F (1936) | 1.16 in (1941) |
| September 11 | 91.0°F (2007) | 37.9°F (1910) | 2.31 in (1920) |
| September 12 | 93.0°F (1924) | 35.1°F (1921) | 1.57 in (1906) |
| September 13 | 88.0°F (1975) | 30.0°F (1907) | 2.25 in (1935) |
| September 14 | 93.9°F (1937) | 34.0°F (1921) | 1.29 in (1996) |
| September 15 | 89.1°F (1957) | 36.0°F (1936) | 1.13 in (1944) |
| September 16 | 93.0°F (1981) | 37.0°F (1901) | 0.87 in (1944) |
| September 17 | 84.9°F (1897) | 37.9°F (1965) | 2.58 in (1997) |
| September 18 | 86.0°F (1991) | 35.1°F (1924) | 1.74 in (2021) |
| September 19 | 87.1°F (1991) | 34.0°F (1947) | 1.31 in (1959) |
| September 20 | 84.9°F (1974) | 36.0°F (1904) | 2.46 in (1959) |
| September 21 | 89.1°F (1952) | 36.0°F (1955) | 2.98 in (1972) |
| September 22 | 91.0°F (1952) | 32.0°F (1926) | 1.94 in (1892) |
| September 23 | 91.9°F (1994) | 37.0°F (1926) | 2.46 in (1978) |
| September 24 | 84.9°F (1919) | 32.0°F (1908) | 1.53 in (1950) |
| September 25 | 88.0°F (1974) | 30.0°F (1902) | 2.00 in (1902) |
| September 26 | 90.0°F (1991) | 33.1°F (1908) | 1.40 in (1902) |
| September 27 | 82.9°F (1936) | 30.0°F (1901) | 1.85 in (1981) |
| September 28 | 88.0°F (1932) | 33.1°F (1919) | 1.31 in (1971) |
| September 29 | 88.0°F (2003) | 30.0°F (1919) | 1.95 in (1937) |
| September 30 | 84.9°F (2008) | 30.0°F (1907) | 2.28 in (2005) |