Weather on March 21
Ontario, CA
55 Years of Data
Avg High
70°F
Avg Low
47°F
Warmest
2026
77°F avg
Coldest
1973
43°F avg
About This Date
March 21st in Ontario, CA typically brings pleasant spring weather, with average highs around 70°F and lows near 47°F. Over 42 years of records, the warmest March 21st was in 2026 (77°F average), while the coldest was 1973 (43°F) — a 34°F range across recorded history. Rain or other precipitation has occurred on about 24% of March 21st dates historically, with the wettest March 21st recording 2.95" of rain. Temperatures on this date have remained relatively stable over the past several decades.
Temperatures on this date have remained relatively stable over the past several decades.
Planning for March 21st in Ontario, CA? Great weather for outdoor activities.
Warming Trend
1.6°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2026warmest | 91° | 63° | 77° | — | — |
| 2025 | 79° | 48° | 63° | — | — |
| 2024 | 73° | 51° | 62° | — | — |
| 2023 | 59° | 45° | 52° | 2.72" | — |
| 2022 | 82° | 47° | 64° | — | — |
| 2021 | 68° | 43° | 55° | — | — |
| 2020 | 66° | 48° | 57° | — | — |
| 2019 | 62° | 52° | 57° | 0.03" | — |
| 2018 | 68° | 54° | 61° | 0.28" | — |
| 2017 | 65° | 53° | 59° | 0.36" | — |
| 2016 | 73° | 51° | 62° | — | — |
| 2015 | 79° | 54° | 66° | — | — |
| 2014 | 70° | 54° | 62° | — | — |
| 2013 | 74° | 51° | 62° | — | — |
| 2012 | 78° | 47° | 62° | — | — |
| 2011 | 55° | 44° | 50° | 2.95" | — |
| 2010 | 80° | 51° | 66° | — | — |
| 2009 | 64° | 52° | 58° | — | — |
| 2008 | 83° | 48° | 65° | — | — |
| 2007 | 64° | 50° | 57° | 0.23" | — |
| 2006 | 58° | 42° | 50° | 0.33" | — |
| 2005 | 68° | 50° | 59° | — | — |
| 2004 | 81° | 51° | 66° | — | — |
| 2003 | 75° | 46° | 61° | — | — |
| 2002 | 84° | 48° | 66° | — | — |
| 2001 | 75° | 52° | 63° | — | — |
| 2000 | 71° | 47° | 59° | — | — |
| 1999 | 66° | 42° | 54° | — | — |
| 1984 | 78° | 42° | 60° | — | — |
| 1983 | 60° | 46° | 53° | 0.86" | — |
| 1982 | 67° | 35° | 51° | — | — |
| 1981 | 64° | 44° | 54° | — | — |
| 1980 | 62° | 44° | 53° | — | — |
| 1979 | 54° | 45° | 49° | 0.08" | — |
| 1978 | 63° | 53° | 58° | 0.76" | — |
| 1977 | 80° | 42° | 61° | — | — |
| 1976 | 84° | 43° | 63° | — | — |
| 1975 | 60° | 42° | 51° | — | — |
| 1974 | 63° | 49° | 56° | — | — |
| 1973coldest | 53° | 33° | 43° | — | — |
| 1972 | 80° | 40° | 60° | — | — |
| 1971 | 69° | 38° | 53° | — | — |
42 years of data from ONTARIO INTL AP