Weather on September 18
Rancho Cucamonga, CA
55 Years of Data
Avg High
88°F
Avg Low
60°F
Warmest
2020
86°F avg
Coldest
1973
61°F avg
About This Date
September 18th in Rancho Cucamonga, CA typically brings warm fall weather, with average highs around 88°F and lows near 60°F — a 28°F daily swing. Over 41 years of records, the warmest September 18th was in 2020 (86°F average), while the coldest was 1973 (61°F) — a 25°F range across recorded history. Rain or other precipitation has occurred on about 2% of September 18th dates historically. The last decade has been 2.8°F warmer on this date compared to 20-30 years ago.
The last decade has been 2.8°F warmer on this date compared to 20-30 years ago.
Planning for September 18th in Rancho Cucamonga, CA? Stay hydrated and seek shade during peak afternoon hours.
Warming Trend
1.0°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 86° | 71° | 79° | 0.23" | — |
| 2024 | 79° | 57° | 68° | — | — |
| 2023 | 80° | 61° | 70° | — | — |
| 2022 | 81° | 62° | 71° | — | — |
| 2021 | 85° | 61° | 73° | — | — |
| 2020warmest | 102° | 70° | 86° | — | — |
| 2019 | 86° | 63° | 74° | — | — |
| 2018 | 91° | 58° | 74° | — | — |
| 2017 | 82° | 60° | 71° | — | — |
| 2016 | 106° | 60° | 83° | — | — |
| 2015 | 94° | 63° | 78° | — | — |
| 2014 | 87° | 66° | 77° | — | — |
| 2013 | 83° | 60° | 71° | — | — |
| 2012 | 94° | 64° | 79° | — | — |
| 2011 | 94° | 57° | 75° | — | — |
| 2010 | 89° | 55° | 72° | — | — |
| 2009 | 99° | 68° | 83° | — | — |
| 2008 | 93° | 66° | 80° | — | — |
| 2007 | 82° | 57° | 70° | — | — |
| 2006 | 95° | 57° | 76° | — | — |
| 2005 | 84° | 56° | 70° | — | — |
| 2004 | 84° | 59° | 72° | — | — |
| 2003 | 93° | 58° | 75° | — | — |
| 2002 | 84° | 60° | 72° | — | — |
| 2001 | 85° | 57° | 71° | — | — |
| 2000 | 98° | 67° | 82° | — | — |
| 1999 | 67° | 58° | 62° | — | — |
| 1998 | 88° | 58° | 73° | — | — |
| 1983 | 96° | 61° | 78° | — | — |
| 1982 | 85° | 61° | 73° | — | — |
| 1981 | 98° | 65° | 81° | — | — |
| 1980 | 100° | 60° | 80° | — | — |
| 1979 | 99° | 65° | 82° | — | — |
| 1978 | 76° | 55° | 65° | — | — |
| 1977 | 82° | 46° | 64° | — | — |
| 1976 | 77° | 50° | 64° | — | — |
| 1975 | 89° | 62° | 76° | — | — |
| 1974 | 89° | 55° | 72° | — | — |
| 1973coldest | 79° | 44° | 61° | — | — |
| 1972 | 77° | 53° | 65° | — | — |
| 1971 | 89° | 56° | 72° | — | — |
41 years of data from ONTARIO INTL AP