September weather in San Marcos, CA
The average temperature in San Marcos in September is 75.0°F (63.1°F–86.9°F). Average precipitation: 0.16 inches.
September is a fall month in San Marcos, and is warmer than the annual average of 65.8°F. Daily temperatures swing about 23.8°F between overnight low and afternoon high. Expect about 1 days with precipitation. Daylight averages about 12h 12m. For travel, September is a comfortable month to visit.
Avg High
86.9°F
Avg Low
63.1°F
Precipitation
0.16 in
Daylight
12h 12m
September records in San Marcos
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 106.0°F (2002) | 55.0°F (1989) | 0.03 in (1983) |
| September 2 | 106.0°F (2017) | 55.9°F (1989) | 0.00 in (1979) |
| September 3 | 108.0°F (1988) | 55.9°F (1989) | 0.10 in (1998) |
| September 4 | 102.9°F (1988) | 54.0°F (2000) | 0.08 in (2019) |
| September 5 | 111.0°F (2020) | 55.9°F (2000) | 0.03 in (1991) |
| September 6 | 115.0°F (2020) | 54.0°F (1985) | 0.06 in (2011) |
| September 7 | 106.0°F (2024) | 55.0°F (1987) | 0.00 in (1979) |
| September 8 | 109.0°F (2024) | 55.9°F (1989) | 0.00 in (1979) |
| September 9 | 104.0°F (2024) | 51.1°F (2000) | 0.16 in (2022) |
| September 10 | 102.0°F (1979) | 51.1°F (2000) | 0.12 in (2022) |
| September 11 | 105.1°F (1979) | 54.0°F (1991) | 0.04 in (2012) |
| September 12 | 102.9°F (2000) | 50.0°F (1985) | 0.00 in (1979) |
| September 13 | 100.0°F (1979) | 54.0°F (1985) | 0.08 in (1987) |
| September 14 | 102.9°F (2012) | 51.1°F (1985) | 0.00 in (1979) |
| September 15 | 104.0°F (1979) | 51.1°F (1994) | 0.75 in (2015) |
| September 16 | 106.0°F (2000) | 53.1°F (1986) | 0.16 in (2015) |
| September 17 | 100.0°F (2000) | 55.0°F (1982) | 0.20 in (1989) |
| September 18 | 102.9°F (2020) | 6.1°F (2021) | 0.51 in (1985) |
| September 19 | 99.0°F (1979) | 53.1°F (1985) | 0.11 in (1989) |
| September 20 | 100.9°F (2015) | 51.1°F (1989) | 0.26 in (2016) |
| September 21 | 102.9°F (2021) | 50.0°F (2007) | 0.36 in (2016) |
| September 22 | 99.0°F (1992) | 50.0°F (1986) | 0.43 in (1987) |
| September 23 | 100.9°F (1982) | 51.1°F (2001) | 0.07 in (2000) |
| September 24 | 102.0°F (1992) | 50.0°F (1993) | 0.10 in (1986) |
| September 25 | 99.0°F (2016) | 50.0°F (2007) | 1.72 in (1997) |
| September 26 | 100.0°F (2010) | 53.1°F (1986) | 0.12 in (1997) |
| September 27 | 109.9°F (2010) | 50.0°F (1986) | 0.03 in (1982) |
| September 28 | 98.1°F (1993) | 51.1°F (1986) | 0.10 in (2019) |
| September 29 | 104.0°F (1992) | 52.0°F (1986) | 0.00 in (1979) |
| September 30 | 107.1°F (2020) | 48.9°F (1982) | 0.08 in (2010) |