Weather on December 21
Simi Valley, CA
55 Years of Data
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.
| 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° | — | — |
Simi Valley, CA Temperature Range by Month
Average monthly highs and lows. The shaded band shows the typical daily temperature range.
Simi Valley, CA Daily Temperature Calendar
Average daily high temperature for every day of the year. Each cell is the climatological mean for that calendar day across 55 years of NOAA data.
Best Time to Visit Simi Valley, CA
Most pleasant months in Simi Valley, CA: January, March, April, May, June, October, November.