Weather on December 21
San Mateo, CA
55 Years of Data
Avg High
56°F
Avg Low
44°F
Warmest
2014
60°F avg
Coldest
1990
34°F avg
About This Date
December 21st in San Mateo, CA typically brings cool winter weather, with average highs around 56°F and lows near 44°F. Over 55 years of records, the warmest December 21st was in 2014 (60°F average), while the coldest was 1990 (34°F) — a 26°F range across recorded history. Rain or other precipitation has occurred on about 42% of December 21st dates historically, with the wettest December 21st recording 4.24" of rain. The last decade has been 1.2°F warmer on this date compared to 20-30 years ago.
The last decade has been 1.2°F warmer on this date compared to 20-30 years ago.
Planning for December 21st in San Mateo, CA? Bring layers as temperatures can vary throughout the day. Consider bringing rain gear or an umbrella.
Warming Trend
1.2°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 62° | 58° | 60° | 0.61" | — |
| 2024 | 59° | 50° | 55° | 0.28" | — |
| 2023 | 62° | 53° | 58° | — | — |
| 2022 | 54° | 41° | 47° | — | — |
| 2021 | 52° | 42° | 47° | 0.64" | — |
| 2020 | 58° | 43° | 50° | — | — |
| 2019 | 62° | 47° | 54° | — | — |
| 2018 | 58° | 47° | 52° | 0.23" | — |
| 2017 | 56° | 40° | 48° | — | — |
| 2016 | 62° | 45° | 53° | — | — |
| 2015 | 59° | 51° | 55° | 2.34" | — |
| 2014warmest | 63° | 58° | 60° | 0.05" | — |
| 2013 | 60° | 47° | 53° | — | — |
| 2012 | 58° | 52° | 55° | 0.81" | — |
| 2011 | 60° | 39° | 50° | — | — |
| 2010 | 58° | 47° | 52° | 0.36" | — |
| 2009 | 58° | 48° | 53° | 0.38" | — |
| 2008 | 52° | 45° | 48° | 0.79" | — |
| 2007 | 57° | 38° | 47° | — | — |
| 2006 | 55° | 44° | 50° | 1.12" | — |
| 2005 | 63° | 54° | 58° | 1.88" | — |
| 2004 | 62° | 44° | 53° | — | — |
| 2003 | 58° | 50° | 54° | — | — |
| 2002 | 56° | 48° | 52° | 0.18" | — |
| 2001 | 52° | 48° | 50° | 0.05" | — |
| 2000 | 58° | 41° | 49° | — | — |
| 1999 | 68° | 49° | 58° | — | — |
| 1998 | 43° | 31° | 37° | — | — |
| 1997 | 56° | 45° | 50° | — | — |
| 1996 | 54° | 49° | 51° | 4.17" | — |
| 1995 | 53° | 43° | 48° | — | — |
| 1994 | 52° | 41° | 46° | — | — |
| 1993 | 46° | 37° | 42° | — | — |
| 1992 | 54° | 47° | 50° | — | — |
| 1991 | 55° | 39° | 47° | — | — |
| 1990coldest | 40° | 28° | 34° | — | — |
| 1989 | 53° | 44° | 49° | — | — |
| 1988 | 55° | 42° | 49° | 0.33" | — |
| 1987 | 53° | 42° | 48° | 0.15" | — |
| 1986 | 55° | 41° | 48° | — | — |
| 1985 | 51° | 38° | 44° | — | — |
| 1984 | 52° | 36° | 44° | — | — |
| 1983 | 52° | 43° | 47° | — | — |
| 1982 | 57° | 50° | 54° | 4.24" | — |
| 1981 | 58° | 48° | 53° | 0.13" | — |
| 1980 | 57° | 50° | 54° | 0.76" | — |
| 1979 | 59° | 48° | 54° | 0.03" | — |
| 1978 | 57° | 30° | 44° | — | — |
| 1977 | 64° | 49° | 56° | — | — |
| 1976 | 58° | 36° | 47° | — | — |
| 1975 | 56° | 40° | 48° | — | — |
| 1974 | 54° | 42° | 48° | — | — |
| 1973 | 60° | 39° | 50° | 1.27" | — |
| 1972 | 56° | 49° | 52° | — | — |
| 1971 | 48° | 31° | 39° | 0.03" | — |
55 years of data from BURLINGAME