September weather in Portola, CA
The average temperature in Portola in September is 58.0°F (37.1°F–78.8°F). Average precipitation: 0.44 inches.
September is a fall month in Portola, and is warmer than the annual average of 46.7°F. Daily temperatures swing about 41.7°F between overnight low and afternoon high. Expect about 2 days with precipitation. Daylight averages about 12h 15m. For travel, September is cool.
Avg High
78.8°F
Avg Low
37.1°F
Precipitation
0.44 in
Snow
0.1 in
September records in Portola
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 99.0°F (1955) | 21.9°F (1939) | 0.28 in (1965) |
| September 2 | 100.0°F (1955) | 23.0°F (1964) | 0.24 in (2023) |
| September 3 | 99.0°F (1955) | 19.9°F (1927) | 0.46 in (2023) |
| September 4 | 98.1°F (1955) | 24.1°F (1929) | 0.30 in (2023) |
| September 5 | 98.1°F (1955) | 19.9°F (1919) | 0.45 in (1978) |
| September 6 | 99.0°F (2022) | 21.0°F (1920) | 0.45 in (1978) |
| September 7 | 99.0°F (2022) | 24.1°F (1920) | 0.07 in (2017) |
| September 8 | 96.1°F (2021) | 21.9°F (1933) | 0.56 in (1985) |
| September 9 | 95.0°F (1944) | 19.9°F (1931) | 0.23 in (1978) |
| September 10 | 95.0°F (1945) | 19.9°F (1931) | 0.56 in (2005) |
| September 11 | 96.1°F (2022) | 21.0°F (1928) | 1.10 in (1976) |
| September 12 | 95.0°F (1945) | 19.0°F (1928) | 1.00 in (1918) |
| September 13 | 93.9°F (1923) | 19.0°F (1928) | 1.00 in (1918) |
| September 14 | 96.1°F (1937) | 21.9°F (1939) | 0.85 in (2017) |
| September 15 | 95.0°F (1979) | 21.9°F (1941) | 0.96 in (1982) |
| September 16 | 93.9°F (1923) | 24.1°F (1939) | 0.75 in (1989) |
| September 17 | 93.9°F (1935) | 24.1°F (1965) | 0.62 in (2019) |
| September 18 | 91.0°F (1974) | 18.0°F (1965) | 0.52 in (1959) |
| September 19 | 91.9°F (1974) | 19.9°F (1947) | 0.53 in (2019) |
| September 20 | 91.0°F (1935) | 18.0°F (1941) | 0.57 in (2022) |
| September 21 | 95.0°F (1992) | 19.9°F (1920) | 0.44 in (1984) |
| September 22 | 91.0°F (1949) | 21.0°F (1960) | 0.42 in (1930) |
| September 23 | 91.0°F (2009) | 18.0°F (1941) | 0.22 in (1983) |
| September 24 | 91.9°F (1936) | 16.0°F (1929) | 0.60 in (1986) |
| September 25 | 91.0°F (2009) | 12.0°F (1929) | 1.02 in (1923) |
| September 26 | 91.9°F (2009) | 16.0°F (1929) | 1.02 in (1998) |
| September 27 | 91.9°F (2010) | 14.0°F (1929) | 0.88 in (1972) |
| September 28 | 90.0°F (2003) | 16.0°F (1929) | 0.28 in (2014) |
| September 29 | 91.9°F (2010) | 15.1°F (1928) | 0.52 in (1994) |
| September 30 | 91.9°F (1980) | 14.0°F (1950) | 0.81 in (1983) |