September weather in Foster City, CA
The average temperature in Foster City in September is 66.8°F (54.3°F–79.3°F). Average precipitation: 0.07 inches.
September is a fall month in Foster City, and is warmer than the annual average of 59.4°F. Daily temperatures swing about 25°F between overnight low and afternoon high. Expect about 1 days with precipitation. Daylight averages about 12h 14m. For travel, September is one of the best months of the year to visit.
Avg High
79.3°F
Avg Low
54.3°F
Precipitation
0.07 in
Daylight
12h 14m
September records in Foster City
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 108.0°F (2017) | 46.0°F (1975) | 0.11 in (1916) |
| September 2 | 108.0°F (2017) | 45.0°F (1975) | 0.00 in (1907) |
| September 3 | 105.1°F (1950) | 46.9°F (1933) | 0.09 in (1907) |
| September 4 | 102.9°F (1950) | 46.0°F (1965) | 0.00 in (1907) |
| September 5 | 108.0°F (2022) | 46.9°F (1932) | 0.14 in (1940) |
| September 6 | 109.9°F (2022) | 46.0°F (1964) | 0.10 in (1912) |
| September 7 | 107.1°F (2020) | 45.0°F (1933) | 0.35 in (1912) |
| September 8 | 102.9°F (1944) | 46.0°F (1964) | 0.14 in (1942) |
| September 9 | 102.9°F (1932) | 44.1°F (1931) | 0.22 in (1999) |
| September 10 | 98.1°F (1944) | 45.0°F (1931) | 0.20 in (1978) |
| September 11 | 102.9°F (1983) | 42.1°F (1931) | 0.03 in (1939) |
| September 12 | 102.9°F (1979) | 44.1°F (1934) | 0.27 in (1963) |
| September 13 | 106.0°F (1971) | 44.1°F (1970) | 0.41 in (1939) |
| September 14 | 106.0°F (1971) | 42.1°F (1970) | 0.01 in (1986) |
| September 15 | 105.1°F (1971) | 44.1°F (1936) | 0.01 in (1908) |
| September 16 | 99.0°F (1971) | 45.0°F (1931) | 0.42 in (1989) |
| September 17 | 97.0°F (1935) | 44.1°F (2006) | 0.08 in (1989) |
| September 18 | 97.0°F (2009) | 44.1°F (1965) | 3.05 in (1959) |
| September 19 | 97.0°F (1943) | 44.1°F (1965) | 0.82 in (1977) |
| September 20 | 102.9°F (1939) | 42.1°F (1965) | 0.02 in (2005) |
| September 21 | 102.0°F (1939) | 42.1°F (1965) | 0.18 in (1983) |
| September 22 | 102.0°F (1939) | 39.0°F (1980) | 0.40 in (1916) |
| September 23 | 100.9°F (1939) | 43.0°F (1972) | 0.12 in (1934) |
| September 24 | 99.0°F (1964) | 39.9°F (1980) | 0.28 in (1982) |
| September 25 | 99.0°F (2019) | 41.0°F (1948) | 0.60 in (2014) |
| September 26 | 99.0°F (1963) | 37.9°F (1980) | 0.66 in (1909) |
| September 27 | 97.0°F (2010) | 42.1°F (1934) | 0.44 in (1972) |
| September 28 | 98.1°F (2010) | 30.9°F (2001) | 0.29 in (1957) |
| September 29 | 96.1°F (1966) | 43.0°F (1955) | 0.11 in (1976) |
| September 30 | 95.0°F (2001) | 41.0°F (1950) | 0.20 in (1916) |