August is one of the warmer months of the year in Fullerton, with average highs near 30.9°C and lows around 18.6°C (mean 24.8°C). It is one of the drier months, averaging 3 mm of rainfall and 49% relative humidity across the period.
August is one of the warmer months of the year in Fullerton. Across 45 years of records, the warmest Augusts in Fullerton were 1998 and 2012 — when the month averaged 26.5°C — while the coldest was 1989 at 22.6°C. Typical August days reach 30.9°C with nights near 18.6°C. The long-term August temperature trend is broadly flat.
August is one of the drier months in Fullerton, averaging 3 mm of rainfall. The wettest August on record was 2023 with 67 mm, while the driest were 2016, 2019 and 2024, among others at 0 mm.
Relative humidity in Fullerton during August averages 49%. The most humid August was 1993 at 55%, and the least humid was 1986 at 38%.
August receives about 6.9 kWh/m²/day of solar energy in Fullerton. The sunniest Augusts were 2010, 2019 and 2024, among others at 7.3 kWh/m²/day, and the cloudiest was 1984 at 6.2.
Average wind speed in Fullerton during August is 1.8 m/s. The windiest Augusts were 1994, 1997 and 2023, among others at 1.9 m/s, while the calmest was 2005 at 1.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 24.7°C | 24.9°C | 24.5°C | 24.5°C | 25.4°C | +0.7°C |
| Avg High | 30.8°C | 31.0°C | 30.6°C | 30.7°C | 31.5°C | +0.7°C |
| Avg Low | 18.5°C | 18.7°C | 18.4°C | 18.3°C | 19.2°C | +0.7°C |
| Avg Rain | 5 mm | 1 mm | 1 mm | 1 mm | 12 mm | +7 mm |
August temperatures in Fullerton have stayed relatively stable across the record.
August has ranged from a record low of 12.5°C (2010) to a record high of 39.4°C (1985).
Rainfall in August is one of the drier months, averaging 3 mm, with a wettest year of 67 mm.
A good time to visit Fullerton
August is a good time to visit Fullerton, with days averaging 30.9°C and nights around 18.6°C (mean 24.8°C, warmer than Fullerton's yearly average) and low rainfall. June and September are marginally more temperate, but August still suits most travellers.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 31.7°C | 25.4°C | 19.0°C | 36.5°C | 15.2°C | 1 mm | 47% | 1.8 m/s | 7 |
| 2024 | 31.5°C | 25.1°C | 18.8°C | 35.3°C | 14.5°C | 0 mm | 46% | 1.7 m/s | 7.3 |
| 2023 🌧️ | 30.7°C | 24.8°C | 18.9°C | 36.6°C | 16.2°C | 67 mm | 53% | 1.9 m/s | 6.8 |
| 2022 | 32.1°C | 26.1°C | 20.2°C | 37.5°C | 17.5°C | 1 mm | 47% | 1.8 m/s | 7 |
| 2021 | 30.6°C | 24.8°C | 18.9°C | 35.2°C | 15.9°C | 1 mm | 49% | 1.7 m/s | 6.7 |
| 2020 | 32.2°C | 25.9°C | 19.7°C | 38.8°C | 14.8°C | 1 mm | 49% | 1.7 m/s | 7.1 |
| 2019 | 31.0°C | 24.6°C | 18.2°C | 34.3°C | 15.1°C | 0 mm | 43% | 1.7 m/s | 7.3 |
| 2018 | 31.4°C | 25.3°C | 19.1°C | 37.3°C | 15.1°C | 0 mm | 51% | 1.8 m/s | 7.2 |
| 2017 | 30.7°C | 24.8°C | 18.9°C | 38.1°C | 14.9°C | 3 mm | 50% | 1.7 m/s | 6.8 |
| 2016 | 30.4°C | 24.1°C | 17.7°C | 34.3°C | 14.6°C | 0 mm | 50% | 1.8 m/s | 7.2 |
| 2015 | 31.3°C | 25.1°C | 19.0°C | 36.4°C | 15.0°C | 0 mm | 52% | 1.8 m/s | 7 |
| 2014 | 30.2°C | 24.1°C | 18.0°C | 34.9°C | 15.1°C | 4 mm | 51% | 1.7 m/s | 7.1 |
| 2013 | 29.7°C | 23.8°C | 17.9°C | 35.3°C | 13.2°C | 1 mm | 46% | 1.7 m/s | 6.9 |
| 2012 | 32.5°C | 26.5°C | 20.4°C | 35.9°C | 15.0°C | 3 mm | 44% | 1.7 m/s | 6.9 |
| 2011 | 30.1°C | 23.7°C | 17.3°C | 37.0°C | 13.7°C | 0 mm | 46% | 1.8 m/s | 7.1 |
| 2010 | 29.3°C | 22.9°C | 16.6°C | 36.7°C | 12.5°C | 0 mm | 46% | 1.7 m/s | 7.3 |
| 2009 | 30.7°C | 24.4°C | 18.0°C | 38.1°C | 14.2°C | 0 mm | 45% | 1.7 m/s | 7.1 |
| 2008 | 31.0°C | 24.8°C | 18.6°C | 34.3°C | 15.8°C | 0 mm | 50% | 1.7 m/s | 7 |
| 2007 | 31.2°C | 25.2°C | 19.1°C | 36.0°C | 14.5°C | 1 mm | 50% | 1.7 m/s | 7.1 |
| 2006 | 30.0°C | 23.8°C | 17.7°C | 33.9°C | 14.0°C | 0 mm | 51% | 1.8 m/s | 7.3 |
| 2005 | 30.6°C | 24.6°C | 18.6°C | 35.3°C | 15.1°C | 1 mm | 50% | 1.6 m/s | 6.8 |
| 2004 | 29.5°C | 23.5°C | 17.4°C | 34.9°C | 14.1°C | 1 mm | 53% | 1.7 m/s | 7 |
| 2003 | 31.7°C | 25.7°C | 19.6°C | 35.3°C | 16.8°C | 2 mm | 47% | 1.8 m/s | 7.2 |
| 2002 | 29.4°C | 23.2°C | 17.0°C | 34.7°C | 14.4°C | 0 mm | 53% | 1.8 m/s | 6.9 |
| 2001 | 30.8°C | 24.6°C | 18.4°C | 34.2°C | 14.6°C | 0 mm | 48% | 1.8 m/s | 7 |
| 2000 | 30.8°C | 24.9°C | 19.1°C | 35.5°C | 15.3°C | 8 mm | 50% | 1.8 m/s | 6.8 |
| 1999 | 30.1°C | 24.0°C | 17.8°C | 35.1°C | 13.8°C | 0 mm | 46% | 1.8 m/s | 7.1 |
| 1998 🔥 | 32.5°C | 26.5°C | 20.5°C | 38.0°C | 16.2°C | 5 mm | 47% | 1.7 m/s | 6.9 |
| 1997 | 31.3°C | 25.2°C | 19.1°C | 38.0°C | 15.6°C | 0 mm | 53% | 1.9 m/s | 7 |
| 1996 | 32.3°C | 25.8°C | 19.3°C | 36.3°C | 14.5°C | 0 mm | 48% | 1.8 m/s | 7.2 |
| 1995 | 31.3°C | 25.3°C | 19.3°C | 35.3°C | 15.2°C | 1 mm | 44% | 1.8 m/s | 6.8 |
| 1994 | 32.3°C | 26.1°C | 19.9°C | 36.1°C | 15.0°C | 0 mm | 47% | 1.9 m/s | 6.7 |
| 1993 | 29.2°C | 23.2°C | 17.2°C | 33.9°C | 14.4°C | 0 mm | 55% | 1.8 m/s | 6.6 |
| 1992 | 31.8°C | 25.7°C | 19.6°C | 36.0°C | 14.3°C | 1 mm | 50% | 1.8 m/s | 6.7 |
| 1991 | 29.3°C | 23.1°C | 17.0°C | 34.1°C | 13.3°C | 1 mm | 53% | 1.8 m/s | 6.5 |
| 1990 | 30.1°C | 23.8°C | 17.5°C | 33.9°C | 13.4°C | 4 mm | 53% | 1.8 m/s | 6.6 |
| 1989 ❄️ | 28.9°C | 22.6°C | 16.3°C | 32.9°C | 13.4°C | 0 mm | 54% | 1.8 m/s | 6.9 |
| 1988 | 29.9°C | 23.8°C | 17.6°C | 33.3°C | 13.9°C | 4 mm | 54% | 1.7 m/s | 6.6 |
| 1987 | 29.6°C | 23.5°C | 17.4°C | 33.6°C | 13.4°C | 1 mm | 51% | 1.8 m/s | 6.7 |
| 1986 | 32.1°C | 25.9°C | 19.7°C | 35.7°C | 16.4°C | 1 mm | 38% | 1.7 m/s | 7 |
| 1985 | 31.0°C | 24.3°C | 17.6°C | 39.4°C | 14.2°C | 0 mm | 44% | 1.8 m/s | 6.9 |
| 1984 | 31.8°C | 25.7°C | 19.7°C | 36.0°C | 17.3°C | 6 mm | 50% | 1.9 m/s | 6.2 |
| 1983 | 31.1°C | 25.5°C | 19.9°C | 36.6°C | 14.9°C | 30 mm | 51% | 1.7 m/s | — |
| 1982 | 31.0°C | 25.1°C | 19.3°C | 35.8°C | 14.5°C | 2 mm | 42% | 1.7 m/s | — |
| 1981 | 32.1°C | 25.6°C | 19.1°C | 38.0°C | 15.4°C | 0 mm | 38% | 1.8 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 30.9°C with lows near 18.6°C (mean 24.8°C), based on 45 years of NASA POWER data.
August averages 3 mm of rainfall in Fullerton, one of the drier months. The wettest on record was 67 mm in 2023.
The hottest August reached 39.4°C in 1985. The coldest dipped to 12.5°C in 2010.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have held steady by about 0°C — but days and nights have moved in opposite directions. Overnight lows rose from 19.1°C to 19.2°C while daytime highs eased from 31.4°C to 31.3°C, narrowing the gap between day and night.
August is one of the warmer months of the year in Fullerton and one of the drier months, so plan for around 30.9°C daytime highs and 18.6°C at night.
Not quite — August is the 12th coolest month in Fullerton, averaging 24.8°C.
For August in Fullerton, pack light, breathable clothing and sun protection, with typical highs of 30.9°C and lows of 18.6°C.
Relative humidity in August averages 49% — relatively dry.
Average wind speed in August is 1.8 m/s. The windiest August on record averaged 1.9 m/s (1984).
The wettest August on record was 2023 with 67 mm. On average, August sees 3 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Fullerton behaves each August, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for August specifically, along with year-by-year records and how the month has changed over the decades.
