Weather on December 21
Simi Valley, CA
55 Years of Data
Avg High
63°F
Avg Low
49°F
Warmest
2020
72°F avg
Coldest
1998
39°F avg
About This Date
December 21st in Simi Valley, CA typically brings mild winter weather, with average highs around 63°F and lows near 49°F. Over 31 years of records, the warmest December 21st was in 2020 (72°F average), while the coldest was 1998 (39°F) — a 33°F range across recorded history. This date has historically been dry, with little recorded precipitation. The last decade has been 6.0°F warmer on this date compared to 20-30 years ago.
The last decade has been 6.0°F warmer on this date compared to 20-30 years ago.
Planning for December 21st in Simi Valley, CA? Great weather for outdoor activities.
Warming Trend
3.6°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 72° | 54° | 63° | — | — |
| 2024 | 70° | 56° | 63° | — | — |
| 2023 | 56° | 53° | 54° | — | — |
| 2022 | 71° | 57° | 64° | — | — |
| 2021 | 66° | 54° | 60° | — | — |
| 2020warmest | 83° | 62° | 72° | — | — |
| 2019 | 67° | 55° | 61° | — | — |
| 2018 | 73° | 54° | 63° | — | — |
| 2017 | 55° | 42° | 49° | — | — |
| 2016 | 62° | 47° | 54° | — | — |
| 2015 | 60° | 46° | 53° | — | — |
| 2014 | 68° | 53° | 61° | — | — |
| 2013 | 60° | 44° | 52° | — | — |
| 2012 | 65° | 47° | 56° | — | — |
| 2011 | 63° | 45° | 54° | — | — |
| 2010 | 54° | 50° | 52° | — | — |
| 2009 | 61° | 51° | 56° | — | — |
| 2008 | 64° | 50° | 57° | — | — |
| 2007 | 55° | 45° | 50° | — | — |
| 2006 | 57° | 37° | 47° | — | — |
| 2005 | 81° | 57° | 69° | — | — |
| 2004 | 61° | 46° | 53° | — | — |
| 2003 | 63° | 46° | 54° | — | — |
| 2002 | 54° | 45° | 49° | — | — |
| 2001 | 54° | 45° | 49° | — | — |
| 2000 | 75° | 56° | 65° | — | — |
| 1999 | 74° | 61° | 67° | — | — |
| 1998coldest | 47° | 32° | 39° | — | — |
| 1997 | 52° | 44° | 48° | — | — |
| 1996 | 57° | 43° | 50° | — | — |
| 1995 | 60° | 45° | 52° | — | — |
31 years of data from SIMI VALLEY CALIFORNIA