Weather on August 18
Rialto, CA
55 Years of Data
Avg High
92°F
Avg Low
65°F
Warmest
1986
95°F avg
Coldest
1976
70°F avg
About This Date
August 18th in Rialto, CA typically brings hot summer weather, with average highs around 92°F and lows near 65°F — a 27°F daily swing. Over 48 years of records, the warmest August 18th was in 1986 (95°F average), while the coldest was 1976 (70°F) — a 25°F range across recorded history. Rain or other precipitation has occurred on about 6% of August 18th dates historically, with the wettest August 18th recording 0.71" of rain.
Planning for August 18th in Rialto, CA? Stay hydrated and seek shade during peak afternoon hours.
Warming Trend
0.9°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 97° | 64° | 80° | — | — |
| 2017 | 88° | 63° | 75° | — | — |
| 2016 | 98° | 70° | 84° | — | — |
| 2015 | 89° | 67° | 78° | — | — |
| 2014 | 95° | 68° | 82° | — | — |
| 2013 | 99° | 72° | 85° | — | — |
| 2012 | 93° | 75° | 84° | — | — |
| 2011 | 95° | 68° | 82° | — | — |
| 2010 | 94° | 73° | 83° | — | — |
| 2009 | 89° | 60° | 75° | — | — |
| 2008 | 87° | 64° | 76° | — | — |
| 2007 | 96° | 69° | 83° | — | — |
| 2006 | 92° | 62° | 77° | — | — |
| 2005 | 90° | 58° | 74° | — | — |
| 2004 | 94° | 65° | 79° | — | — |
| 2003 | 101° | 68° | 84° | — | — |
| 2002 | 89° | 59° | 74° | — | — |
| 2001 | 101° | 70° | 85° | — | — |
| 2000 | 95° | 66° | 81° | — | — |
| 1999 | 97° | 67° | 82° | — | — |
| 1998 | 90° | 58° | 74° | — | — |
| 1997 | 97° | 59° | 78° | — | — |
| 1996 | 92° | 61° | 76° | — | — |
| 1995 | 93° | 61° | 77° | — | — |
| 1994 | 94° | 70° | 82° | — | — |
| 1993 | 93° | 60° | 77° | — | — |
| 1992 | 99° | 74° | 86° | — | — |
| 1991 | 87° | 60° | 74° | — | — |
| 1990 | 85° | 61° | 73° | — | — |
| 1989 | 86° | 57° | 72° | — | — |
| 1988 | 92° | 61° | 76° | — | — |
| 1987 | 86° | 58° | 72° | — | — |
| 1986warmest | 98° | 92° | 95° | 0.05" | — |
| 1985 | 88° | 61° | 74° | — | — |
| 1984 | 87° | 73° | 80° | — | — |
| 1983 | 73° | 68° | 71° | 0.71" | — |
| 1982 | 102° | 66° | 84° | — | — |
| 1981 | 95° | 65° | 80° | — | — |
| 1980 | 83° | 63° | 73° | — | — |
| 1979 | 90° | 65° | 77° | — | — |
| 1978 | 86° | 67° | 76° | — | — |
| 1977 | 88° | 67° | 77° | 0.2" | — |
| 1976coldest | 83° | 58° | 70° | — | — |
| 1975 | 88° | 57° | 72° | — | — |
| 1974 | 96° | 59° | 78° | — | — |
| 1973 | 104° | 67° | 85° | — | — |
| 1972 | 84° | 60° | 72° | — | — |
| 1971 | 99° | 65° | 82° | — | — |
48 years of data from FONTANA 5 N