Weather on August 18
San Marcos, CA
55 Years of Data
Avg High
86°F
Avg Low
64°F
Warmest
2020
90°F avg
Coldest
1975
68°F avg
About This Date
August 18th in San Marcos, CA typically brings warm summer weather, with average highs around 86°F and lows near 64°F. Over 55 years of records, the warmest August 18th was in 2020 (90°F average), while the coldest was 1975 (68°F) — a 22°F range across recorded history. Rain or other precipitation has occurred on about 5% of August 18th dates historically. The last decade has been 2.4°F warmer on this date compared to 20-30 years ago.
The last decade has been 2.4°F warmer on this date compared to 20-30 years ago.
Planning for August 18th in San Marcos, CA? Stay hydrated and seek shade during peak afternoon hours.
Warming Trend
1.1°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 91° | 64° | 78° | — | — |
| 2024 | 90° | 63° | 76° | — | — |
| 2023 | 91° | 63° | 77° | — | — |
| 2022 | 92° | 68° | 80° | — | — |
| 2021 | 79° | 68° | 73° | — | — |
| 2020warmest | 107° | 73° | 90° | — | — |
| 2019 | 86° | 63° | 74° | — | — |
| 2018 | 89° | 72° | 80° | — | — |
| 2017 | 84° | 64° | 74° | — | — |
| 2016 | 93° | 66° | 80° | — | — |
| 2015 | 89° | 70° | 79° | — | — |
| 2014 | 91° | 67° | 79° | — | — |
| 2013 | 91° | 63° | 77° | — | — |
| 2012 | 93° | 75° | 84° | — | — |
| 2011 | 86° | 61° | 73° | — | — |
| 2010 | 84° | 69° | 77° | — | — |
| 2009 | 72° | 64° | 68° | — | — |
| 2008 | 73° | 66° | 70° | — | — |
| 2007 | 80° | 68° | 74° | — | — |
| 2006 | 75° | 65° | 70° | — | — |
| 2005 | 74° | 64° | 69° | — | — |
| 2004 | 85° | 61° | 73° | — | — |
| 2003 | 92° | 65° | 78° | — | — |
| 2002 | 79° | 63° | 71° | — | — |
| 2001 | 97° | 67° | 82° | — | — |
| 2000 | 94° | 66° | 80° | — | — |
| 1999 | 89° | 62° | 76° | — | — |
| 1998 | 87° | 64° | 76° | — | — |
| 1997 | 92° | 61° | 76° | — | — |
| 1996 | 88° | 67° | 77° | — | — |
| 1995 | 87° | 58° | 72° | — | — |
| 1994 | 90° | 69° | 79° | — | — |
| 1993 | 87° | 62° | 75° | — | — |
| 1992 | 99° | 70° | 84° | — | — |
| 1991 | 85° | 61° | 73° | — | — |
| 1990 | 81° | 64° | 72° | — | — |
| 1989 | 80° | 62° | 71° | — | — |
| 1988 | 81° | 59° | 70° | — | — |
| 1987 | 78° | 61° | 69° | — | — |
| 1986 | 98° | 78° | 88° | — | — |
| 1985 | 82° | 64° | 73° | — | — |
| 1984 | 81° | 68° | 74° | 0.23" | — |
| 1983 | 73° | 68° | 71° | 0.33" | — |
| 1982 | 88° | 61° | 74° | — | — |
| 1981 | 86° | 64° | 75° | — | — |
| 1980 | 80° | 61° | 70° | — | — |
| 1979 | 82° | 62° | 72° | — | — |
| 1978 | 86° | 57° | 72° | — | — |
| 1977 | 79° | 66° | 72° | 0.28" | — |
| 1976 | 80° | 63° | 71° | — | — |
| 1975coldest | 81° | 55° | 68° | — | — |
| 1974 | 86° | 54° | 70° | — | — |
| 1973 | 93° | 62° | 78° | — | — |
| 1972 | 79° | 63° | 71° | — | — |
| 1971 | 88° | 61° | 74° | — | — |
55 years of data from ESCONDIDO #2