Weather on September 21
San Ramon, CA
55 Years of Data
Avg High
82°F
Avg Low
57°F
Warmest
2003
84°F avg
Coldest
2017
52°F avg
About This Date
September 21st in San Ramon, CA typically brings warm fall weather, with average highs around 82°F and lows near 57°F — a 25°F daily swing. Over 55 years of records, the warmest September 21st was in 2003 (84°F average), while the coldest was 2017 (52°F) — a 32°F range across recorded history. Rain or other precipitation has occurred on about 4% of September 21st dates historically. The last decade has been 4.7°F cooler on this date compared to 20-30 years ago.
The last decade has been 4.7°F cooler on this date compared to 20-30 years ago.
Planning for September 21st in San Ramon, CA? Stay hydrated and seek shade during peak afternoon hours.
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 82° | 64° | 73° | — | — |
| 2024 | 81° | 50° | 65° | — | — |
| 2023 | 72° | 49° | 60° | — | — |
| 2022 | 65° | 53° | 59° | 0.15" | — |
| 2021 | 87° | 58° | 72° | — | — |
| 2020 | 84° | 67° | 75° | — | — |
| 2019 | 76° | 63° | 69° | — | — |
| 2018 | 84° | 66° | 75° | — | — |
| 2017coldest | 61° | 43° | 52° | — | — |
| 2016 | 81° | 57° | 69° | — | — |
| 2015 | 93° | 76° | 84° | — | — |
| 2014 | 78° | 55° | 67° | — | — |
| 2013 | 80° | 47° | 63° | 0.08" | — |
| 2012 | 78° | 64° | 71° | — | — |
| 2011 | 90° | 73° | 81° | — | — |
| 2010 | 74° | 48° | 61° | — | — |
| 2009 | 89° | 67° | 78° | — | — |
| 2008 | 68° | 49° | 58° | — | — |
| 2007 | 70° | 48° | 59° | — | — |
| 2006 | 88° | 56° | 72° | — | — |
| 2005 | 85° | 53° | 69° | — | — |
| 2004 | 83° | 53° | 68° | — | — |
| 2003warmest | 102° | 66° | 84° | — | — |
| 2002 | 97° | 63° | 80° | — | — |
| 2001 | 85° | 52° | 68° | — | — |
| 2000 | 75° | 58° | 66° | — | — |
| 1999 | 91° | 54° | 72° | — | — |
| 1998 | 73° | 51° | 62° | — | — |
| 1997 | 91° | 59° | 75° | — | — |
| 1996 | 88° | 57° | 72° | — | — |
| 1995 | 86° | 56° | 71° | — | — |
| 1994 | 89° | 56° | 72° | — | — |
| 1993 | 79° | 51° | 65° | — | — |
| 1992 | 92° | 55° | 73° | — | — |
| 1991 | 86° | 59° | 73° | — | — |
| 1990 | 85° | 59° | 72° | — | — |
| 1989 | 74° | 56° | 65° | — | — |
| 1988 | 74° | 49° | 61° | — | — |
| 1987 | 92° | 68° | 80° | — | — |
| 1986 | 69° | 48° | 59° | — | — |
| 1985 | 85° | 61° | 73° | — | — |
| 1984 | 71° | 65° | 68° | — | — |
| 1983 | 89° | 66° | 78° | — | — |
| 1982 | 76° | 52° | 64° | — | — |
| 1981 | 80° | 55° | 68° | — | — |
| 1980 | 69° | 52° | 60° | — | — |
| 1979 | 88° | 62° | 75° | — | — |
| 1978 | 80° | 57° | 69° | — | — |
| 1977 | 75° | 55° | 65° | — | — |
| 1976 | 83° | 52° | 67° | — | — |
| 1975 | 89° | 62° | 76° | — | — |
| 1974 | 92° | 66° | 79° | — | — |
| 1973 | 71° | 45° | 58° | — | — |
| 1972 | 85° | 51° | 68° | — | — |
| 1971 | 86° | 58° | 72° | — | — |
55 years of data from LIVERMORE CALIFORNIA