Weather on December 21
Rialto, CA
55 Years of Data
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.
| 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° | — | — |
Rialto, CA Temperature Range by Month
Average monthly highs and lows. The shaded band shows the typical daily temperature range.
Rialto, CA Monthly Precipitation
Average rainfall and snowfall per month, in inches.
Rialto, 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 Rialto, CA
Rialto, CA has no months that meet our "pleasant" threshold — every season has tradeoffs.