Weather on December 31
Ontario, CA
55 Years of Data
Avg High
63°F
Avg Low
42°F
Warmest
1980
61°F avg
Coldest
2010
42°F avg
About This Date
December 31st in Ontario, CA typically brings mild winter weather, with average highs around 63°F and lows near 42°F. Over 40 years of records, the warmest December 31st was in 1980 (61°F average), while the coldest was 2010 (42°F) — a 19°F range across recorded history. Rain or other precipitation has occurred on about 18% of December 31st dates historically, with the wettest December 31st recording 1.6" of rain. The last decade has been 2.5°F warmer on this date compared to 20-30 years ago.
The last decade has been 2.5°F warmer on this date compared to 20-30 years ago.
Planning for December 31st in Ontario, CA? Great weather for outdoor activities.
Warming Trend
0.5°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 64° | 53° | 59° | 0.76" | — |
| 2024 | 66° | 44° | 55° | — | — |
| 2023 | 59° | 49° | 54° | — | — |
| 2022 | 57° | 53° | 55° | — | — |
| 2021 | 60° | 43° | 51° | — | — |
| 2020 | 66° | 38° | 52° | — | — |
| 2019 | 71° | 45° | 58° | — | — |
| 2018 | 60° | 44° | 52° | — | — |
| 2017 | 71° | 47° | 59° | — | — |
| 2016 | 54° | 44° | 49° | 0.41" | — |
| 2015 | 64° | 34° | 49° | — | — |
| 2014 | 52° | 32° | 42° | — | — |
| 2013 | 73° | 42° | 58° | — | — |
| 2012 | 57° | 33° | 45° | — | — |
| 2011 | 79° | 43° | 61° | — | — |
| 2010coldest | 53° | 30° | 42° | — | — |
| 2009 | 66° | 40° | 53° | 0.03" | — |
| 2008 | 70° | 45° | 57° | — | — |
| 2007 | 74° | 38° | 56° | — | — |
| 2006 | 63° | 37° | 50° | — | — |
| 2005 | 56° | 46° | 51° | 1.52" | — |
| 2004 | 54° | 41° | 47° | 1.6" | — |
| 2003 | 64° | 38° | 51° | — | — |
| 2002 | 59° | 42° | 51° | — | — |
| 2001 | 59° | 50° | 55° | — | — |
| 2000 | 76° | 39° | 57° | — | — |
| 1999 | 53° | 46° | 50° | 0.66" | — |
| 1998 | 63° | 44° | 53° | — | — |
| 1983 | 73° | 44° | 59° | — | — |
| 1981 | 54° | 48° | 51° | — | — |
| 1980warmest | 78° | 44° | 61° | — | — |
| 1979 | 70° | 48° | 59° | — | — |
| 1978 | 62° | 38° | 50° | — | — |
| 1977 | 55° | 45° | 50° | — | — |
| 1976 | 58° | 44° | 51° | 0.23" | — |
| 1975 | 58° | 38° | 48° | — | — |
| 1974 | 52° | 41° | 46° | — | — |
| 1973 | 61° | 39° | 50° | — | — |
| 1972 | 58° | 33° | 45° | — | — |
| 1971 | 61° | 36° | 48° | — | — |
40 years of data from ONTARIO INTL AP