Weather on December 21
Rialto, CA
55 Years of Data
Avg High
63°F
Avg Low
43°F
Warmest
2005
72°F avg
Coldest
1990
34°F avg
About This Date
December 21st in Rialto, CA typically brings mild winter weather, with average highs around 63°F and lows near 43°F. Over 47 years of records, the warmest December 21st was in 2005 (72°F average), while the coldest was 1990 (34°F) — a 38°F range across recorded history. Rain or other precipitation has occurred on about 6% of December 21st dates historically, with the wettest December 21st recording 3.63" of rain.
Planning for December 21st in Rialto, CA? Great weather for outdoor activities.
Cooling Trend
0.4°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 77° | 43° | 60° | — | — |
| 2016 | 61° | 45° | 53° | — | — |
| 2015 | 54° | 39° | 46° | — | — |
| 2014 | 64° | 47° | 55° | — | — |
| 2013 | 55° | 39° | 47° | — | — |
| 2012 | 64° | 39° | 52° | — | — |
| 2011 | 61° | 42° | 51° | — | — |
| 2010 | 52° | 47° | 49° | — | — |
| 2009 | 61° | 48° | 54° | — | — |
| 2008 | 61° | 45° | 53° | — | — |
| 2007 | 52° | 43° | 47° | — | — |
| 2006 | 61° | 37° | 49° | — | — |
| 2005warmest | 86° | 58° | 72° | — | — |
| 2004 | 70° | 42° | 56° | — | — |
| 2003 | 64° | 48° | 56° | — | — |
| 2002 | 47° | 43° | 45° | — | — |
| 2001 | 45° | 38° | 41° | — | — |
| 2000 | 79° | 48° | 63° | — | — |
| 1999 | 74° | 56° | 65° | — | — |
| 1998 | 47° | 35° | 41° | — | — |
| 1997 | 50° | 40° | 45° | — | — |
| 1996 | 52° | 39° | 45° | — | — |
| 1995 | 67° | 39° | 53° | — | — |
| 1994 | 72° | 54° | 63° | — | — |
| 1993 | 63° | 45° | 54° | — | — |
| 1992 | 59° | 42° | 51° | — | — |
| 1991 | 67° | 46° | 56° | — | — |
| 1990coldest | 42° | 26° | 34° | — | — |
| 1989 | 63° | 36° | 49° | — | — |
| 1988 | 59° | 46° | 53° | 3.63" | — |
| 1987 | 65° | 36° | 50° | — | — |
| 1986 | 68° | 46° | 57° | — | — |
| 1985 | 78° | 43° | 60° | — | — |
| 1984 | 62° | 35° | 49° | — | — |
| 1983 | 58° | 48° | 53° | — | — |
| 1982 | 61° | 35° | 48° | — | — |
| 1981 | 64° | 52° | 58° | 0.03" | — |
| 1980 | 80° | 44° | 62° | — | — |
| 1979 | 60° | 50° | 55° | — | — |
| 1978 | 68° | 32° | 50° | — | — |
| 1977 | 61° | 43° | 52° | 0.2" | — |
| 1976 | 69° | 38° | 53° | — | — |
| 1975 | 62° | 52° | 57° | — | — |
| 1974 | 76° | 41° | 58° | — | — |
| 1973 | 67° | 37° | 52° | — | — |
| 1972 | 80° | 45° | 62° | — | — |
| 1971 | 61° | 37° | 49° | — | — |
47 years of data from FONTANA 5 N