December weather in San Marcos, CA
The average temperature in San Marcos in December is 55.9°F (43.8°F–68.0°F). Average precipitation: 2.14 inches.
December is a winter month in San Marcos, and is cooler than the annual average of 65.8°F. Daily temperatures swing about 24.2°F between overnight low and afternoon high. Expect about 6 days with precipitation. Daylight averages about 9h 49m. For travel, December is a comfortable month to visit.
Avg High
68.0°F
Avg Low
43.8°F
Precipitation
2.14 in
Daylight
9h 49m
December records in San Marcos
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| December 1 | 84.0°F (1979) | 28.9°F (1991) | 0.18 in (1997) |
| December 2 | 82.0°F (1988) | 32.0°F (1991) | 0.10 in (2018) |
| December 3 | 82.0°F (1979) | 32.0°F (1982) | 0.85 in (2014) |
| December 4 | 90.0°F (1979) | 35.1°F (2004) | 1.33 in (2019) |
| December 5 | 87.1°F (1979) | 35.1°F (1983) | 0.62 in (1987) |
| December 6 | 89.1°F (1979) | 35.1°F (1983) | 0.72 in (1986) |
| December 7 | 86.0°F (1989) | 32.0°F (1998) | 1.32 in (1992) |
| December 8 | 86.0°F (1990) | 36.0°F (1998) | 0.73 in (1984) |
| December 9 | 86.0°F (2025) | 30.9°F (1994) | 0.11 in (2021) |
| December 10 | 87.1°F (2025) | 32.0°F (1979) | 0.68 in (1996) |
| December 11 | 86.0°F (2025) | 35.1°F (1986) | 0.77 in (1996) |
| December 12 | 86.0°F (2010) | 30.0°F (1985) | 0.82 in (2014) |
| December 13 | 84.0°F (2010) | 30.9°F (1985) | 1.73 in (2012) |
| December 14 | 80.1°F (1996) | 34.0°F (1979) | 1.60 in (2021) |
| December 15 | 82.0°F (1980) | 28.9°F (1987) | 0.11 in (2012) |
| December 16 | 88.0°F (1980) | 33.1°F (1979) | 2.01 in (2016) |
| December 17 | 84.0°F (1979) | 32.0°F (1984) | 0.96 in (1987) |
| December 18 | 86.0°F (2024) | 34.0°F (1982) | 0.51 in (1984) |
| December 19 | 82.9°F (2024) | 32.0°F (2006) | 0.97 in (1984) |
| December 20 | 82.0°F (2020) | 28.9°F (1992) | 1.24 in (2010) |
| December 21 | 84.0°F (2005) | 32.0°F (1992) | 2.04 in (2010) |
| December 22 | 81.0°F (1989) | 30.9°F (1990) | 3.02 in (2010) |
| December 23 | 89.1°F (1989) | 26.1°F (1990) | 1.16 in (1982) |
| December 24 | 87.1°F (1989) | 30.0°F (1987) | 1.55 in (2021) |
| December 25 | 86.0°F (2005) | 28.0°F (1987) | 1.82 in (1983) |
| December 26 | 84.9°F (2022) | 27.0°F (1987) | 1.32 in (2019) |
| December 27 | 82.9°F (2013) | 30.0°F (1987) | 0.97 in (1984) |
| December 28 | 82.9°F (2017) | 28.0°F (2007) | 0.76 in (2022) |
| December 29 | 90.0°F (1980) | 32.0°F (1988) | 1.10 in (2004) |
| December 30 | 86.0°F (1980) | 30.0°F (1988) | 0.85 in (1992) |
| December 31 | 81.0°F (1980) | 28.9°F (1982) | 0.66 in (2014) |