Weather on August 31
Ontario, CA
55 Years of Data
Avg High
94°F
Avg Low
63°F
Warmest
2017
95°F avg
Coldest
1971
65°F avg
About This Date
August 31st in Ontario, CA typically brings hot summer weather, with average highs around 94°F and lows near 63°F — a 31°F daily swing. Over 42 years of records, the warmest August 31st was in 2017 (95°F average), while the coldest was 1971 (65°F) — a 30°F range across recorded history. Rain or other precipitation has occurred on about 5% of August 31st dates historically. The last decade has been 4.5°F warmer on this date compared to 20-30 years ago.
The last decade has been 4.5°F warmer on this date compared to 20-30 years ago.
Planning for August 31st in Ontario, CA? Stay hydrated and seek shade during peak afternoon hours.
Warming Trend
2.0°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 101° | 70° | 85° | — | — |
| 2024 | 94° | 63° | 78° | — | — |
| 2023 | 94° | 69° | 81° | — | — |
| 2022 | 108° | 72° | 90° | — | — |
| 2021 | 84° | 67° | 75° | — | — |
| 2020 | 90° | 60° | 75° | — | — |
| 2019 | 99° | 68° | 83° | — | — |
| 2018 | 92° | 63° | 77° | — | — |
| 2017warmest | 112° | 78° | 95° | 0.05" | — |
| 2016 | 101° | 69° | 85° | — | — |
| 2015 | 91° | 66° | 79° | — | — |
| 2014 | 95° | 68° | 82° | — | — |
| 2013 | 96° | 77° | 87° | — | — |
| 2012 | 96° | 70° | 83° | — | — |
| 2011 | 91° | 59° | 75° | — | — |
| 2010 | 89° | 60° | 75° | — | — |
| 2009 | 101° | 71° | 86° | — | — |
| 2008 | 90° | 67° | 78° | — | — |
| 2007 | 108° | 78° | 93° | — | — |
| 2006 | 97° | 65° | 81° | — | — |
| 2005 | 91° | 60° | 76° | — | — |
| 2004 | 101° | 64° | 82° | — | — |
| 2003 | 94° | 63° | 78° | — | — |
| 2002 | 98° | 64° | 81° | — | — |
| 2001 | 89° | 60° | 75° | — | — |
| 2000 | 78° | 62° | 70° | — | — |
| 1999 | 88° | 56° | 72° | — | — |
| 1998 | 105° | 74° | 89° | 0.33" | — |
| 1984 | 98° | 65° | 81° | — | — |
| 1983 | 96° | 61° | 78° | — | — |
| 1982 | 97° | 59° | 78° | — | — |
| 1981 | 93° | 59° | 76° | — | — |
| 1980 | 86° | 53° | 70° | — | — |
| 1979 | 86° | 53° | 70° | — | — |
| 1978 | 95° | 58° | 76° | — | — |
| 1977 | 84° | 61° | 72° | — | — |
| 1976 | 100° | 66° | 83° | — | — |
| 1975 | 92° | 54° | 73° | — | — |
| 1974 | 94° | 56° | 75° | — | — |
| 1973 | 80° | 50° | 65° | — | — |
| 1972 | 90° | 61° | 75° | — | — |
| 1971coldest | 85° | 45° | 65° | — | — |
42 years of data from ONTARIO INTL AP