Weather on April 21
Ontario, CA
55 Years of Data
Avg High
77°F
Avg Low
50°F
Warmest
2009
83°F avg
Coldest
2010
51°F avg
About This Date
April 21st in Ontario, CA typically brings pleasant spring weather, with average highs around 77°F and lows near 50°F — a 27°F daily swing. Over 42 years of records, the warmest April 21st was in 2009 (83°F average), while the coldest was 2010 (51°F) — a 32°F range across recorded history. Rain or other precipitation has occurred on about 12% of April 21st dates historically, with the wettest April 21st recording 2.08" of rain. The last decade has been 5.4°F warmer on this date compared to 20-30 years ago.
The last decade has been 5.4°F warmer on this date compared to 20-30 years ago.
Planning for April 21st in Ontario, CA? Great weather for outdoor activities.
Warming Trend
1.5°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 79° | 53° | 66° | — | — |
| 2024 | 84° | 53° | 69° | — | — |
| 2023 | 90° | 53° | 71° | — | — |
| 2022 | 72° | 49° | 60° | 0.03" | — |
| 2021 | 63° | 54° | 58° | — | — |
| 2020 | 74° | 54° | 64° | — | — |
| 2019 | 74° | 57° | 65° | — | — |
| 2018 | 90° | 50° | 70° | — | — |
| 2017 | 93° | 56° | 74° | — | — |
| 2016 | 87° | 56° | 71° | — | — |
| 2015 | 66° | 55° | 61° | — | — |
| 2014 | 88° | 57° | 72° | — | — |
| 2013 | 89° | 57° | 73° | — | — |
| 2012 | 91° | 57° | 74° | — | — |
| 2011 | 69° | 54° | 61° | — | — |
| 2010coldest | 60° | 42° | 51° | — | — |
| 2009warmest | 100° | 66° | 83° | — | — |
| 2008 | 71° | 46° | 59° | — | — |
| 2007 | 63° | 47° | 55° | — | — |
| 2006 | 73° | 55° | 64° | — | — |
| 2005 | 83° | 50° | 66° | — | — |
| 2004 | 72° | 51° | 61° | — | — |
| 2003 | 65° | 50° | 57° | — | — |
| 2002 | 82° | 45° | 63° | — | — |
| 2001 | 64° | 45° | 54° | 0.61" | — |
| 2000 | 65° | 52° | 58° | 0.03" | — |
| 1999 | 65° | 53° | 59° | — | — |
| 1998 | 95° | 50° | 73° | — | — |
| 1984 | 81° | 49° | 65° | — | — |
| 1983 | 63° | 48° | 55° | 2.08" | — |
| 1982 | 75° | 58° | 66° | — | — |
| 1981 | 78° | 44° | 61° | — | — |
| 1980 | 69° | 53° | 61° | 0.15" | — |
| 1979 | 81° | 45° | 63° | — | — |
| 1978 | 75° | 40° | 57° | — | — |
| 1977 | 80° | 46° | 63° | — | — |
| 1976 | 81° | 51° | 66° | — | — |
| 1975 | 72° | 42° | 57° | — | — |
| 1974 | 81° | 42° | 61° | — | — |
| 1973 | 75° | 43° | 59° | — | — |
| 1972 | 80° | 43° | 61° | — | — |
| 1971 | 59° | 44° | 52° | — | — |
42 years of data from ONTARIO INTL AP