Weather on December 20
Ontario, CA
55 Years of Data
Avg High
67°F
Avg Low
42°F
Warmest
1999
66°F avg
Coldest
1978
45°F avg
About This Date
December 20th in Ontario, CA typically brings mild winter weather, with average highs around 67°F and lows near 42°F — a 25°F daily swing. Over 41 years of records, the warmest December 20th was in 1999 (66°F average), while the coldest was 1978 (45°F) — a 21°F range across recorded history. Rain or other precipitation has occurred on about 15% of December 20th dates historically, with the wettest December 20th recording 1.75" of rain. The last decade has been 2.9°F warmer on this date compared to 20-30 years ago.
The last decade has been 2.9°F warmer on this date compared to 20-30 years ago.
Planning for December 20th in Ontario, CA? Great weather for outdoor activities.
Warming Trend
0.7°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 67° | 45° | 56° | — | — |
| 2024 | 78° | 51° | 65° | — | — |
| 2023 | 68° | 55° | 62° | 0.91" | — |
| 2022 | 66° | 39° | 53° | — | — |
| 2021 | 69° | 37° | 53° | — | — |
| 2020 | 82° | 39° | 61° | — | — |
| 2019 | 76° | 42° | 59° | — | — |
| 2018 | 79° | 48° | 63° | — | — |
| 2017 | 62° | 43° | 52° | — | — |
| 2016 | 75° | 37° | 56° | — | — |
| 2015 | 59° | 44° | 52° | — | — |
| 2014 | 59° | 46° | 53° | — | — |
| 2013 | 61° | 39° | 50° | — | — |
| 2012 | 65° | 33° | 49° | — | — |
| 2011 | 64° | 40° | 52° | — | — |
| 2010 | 59° | 52° | 55° | 0.74" | — |
| 2009 | 70° | 46° | 58° | — | — |
| 2008 | 59° | 35° | 47° | — | — |
| 2007 | 58° | 48° | 53° | 0.94" | — |
| 2006 | 59° | 36° | 47° | — | — |
| 2005 | 77° | 47° | 62° | — | — |
| 2004 | 71° | 43° | 57° | — | — |
| 2003 | 64° | 47° | 55° | — | — |
| 2002 | 56° | 44° | 50° | 1.75" | — |
| 2001 | 56° | 42° | 49° | 0.36" | — |
| 2000 | 73° | 40° | 56° | — | — |
| 1999warmest | 80° | 51° | 66° | — | — |
| 1998 | 54° | 39° | 46° | 0.03" | — |
| 1983 | 58° | 47° | 52° | — | — |
| 1982 | 75° | 38° | 56° | — | — |
| 1981 | 65° | 40° | 52° | — | — |
| 1980 | 77° | 42° | 60° | — | — |
| 1979 | 64° | 39° | 52° | — | — |
| 1978coldest | 58° | 32° | 45° | — | — |
| 1977 | 67° | 41° | 54° | — | — |
| 1976 | 67° | 40° | 53° | — | — |
| 1975 | 69° | 37° | 53° | — | — |
| 1974 | 71° | 41° | 56° | — | — |
| 1973 | 68° | 37° | 53° | — | — |
| 1972 | 75° | 46° | 61° | — | — |
| 1971 | 60° | 34° | 47° | — | — |
41 years of data from ONTARIO INTL AP