September weather in Half Moon Bay, CA
The average temperature in Half Moon Bay in September is 58.8°F (51.3°F–66.4°F). Average precipitation: 0.21 inches.
September is a fall month in Half Moon Bay, and is warmer than the annual average of 54.9°F. Daily temperatures swing about 15.1°F between overnight low and afternoon high. Expect about 6 days with precipitation. Daylight averages about 12h 14m. For travel, September is one of the best months of the year to visit.
Avg High
66.4°F
Avg Low
51.3°F
Precipitation
0.21 in
Daylight
12h 14m
September records in Half Moon Bay
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 81.0°F (1947) | 42.1°F (1984) | 0.30 in (2000) |
| September 2 | 82.9°F (2017) | 39.9°F (1975) | 0.14 in (1985) |
| September 3 | 87.1°F (2017) | 41.0°F (2012) | 0.02 in (1991) |
| September 4 | 90.0°F (1961) | 39.9°F (1988) | 0.12 in (1962) |
| September 5 | 82.9°F (1961) | 43.0°F (1970) | 0.08 in (1940) |
| September 6 | 81.0°F (2022) | 41.0°F (2010) | 0.22 in (1940) |
| September 7 | 82.9°F (2020) | 41.0°F (1982) | 0.10 in (1980) |
| September 8 | 90.0°F (1944) | 43.0°F (2004) | 0.16 in (1942) |
| September 9 | 79.0°F (1979) | 45.0°F (2004) | 0.20 in (1999) |
| September 10 | 89.1°F (1979) | 44.1°F (2002) | 0.11 in (2003) |
| September 11 | 93.9°F (1983) | 43.0°F (2002) | 0.05 in (2004) |
| September 12 | 81.0°F (1983) | 43.0°F (1946) | 0.08 in (2017) |
| September 13 | 82.0°F (2000) | 41.0°F (1988) | 0.09 in (1963) |
| September 14 | 80.1°F (1952) | 42.1°F (1965) | 0.44 in (1939) |
| September 15 | 84.0°F (1951) | 39.9°F (2002) | 0.19 in (1986) |
| September 16 | 90.0°F (1958) | 42.1°F (1993) | 0.32 in (1982) |
| September 17 | 82.0°F (1988) | 39.0°F (2006) | 0.50 in (1961) |
| September 18 | 89.1°F (1946) | 39.9°F (1970) | 1.10 in (1959) |
| September 19 | 86.0°F (1939) | 41.0°F (1993) | 2.56 in (1959) |
| September 20 | 90.0°F (1939) | 42.1°F (2006) | 0.31 in (1973) |
| September 21 | 86.0°F (1939) | 39.0°F (2004) | 0.77 in (2013) |
| September 22 | 88.0°F (1939) | 39.0°F (2004) | 0.15 in (1990) |
| September 23 | 91.0°F (1978) | 39.9°F (2004) | 1.20 in (1986) |
| September 24 | 91.0°F (1954) | 39.9°F (2004) | 0.43 in (1982) |
| September 25 | 91.9°F (2019) | 37.0°F (2005) | 0.91 in (1982) |
| September 26 | 90.0°F (1970) | 39.9°F (2004) | 0.43 in (1986) |
| September 27 | 89.1°F (1966) | 41.0°F (2004) | 0.60 in (1972) |
| September 28 | 91.0°F (1958) | 39.9°F (2013) | 0.71 in (1957) |
| September 29 | 84.9°F (1978) | 39.0°F (2007) | 0.32 in (1962) |
| September 30 | 91.9°F (2001) | 35.1°F (2007) | 0.60 in (1983) |