October is one of the warmer months of the year in Fullerton, with average highs near 26.1°C and lows around 14.4°C (mean 20.3°C). It is one of the drier months, averaging 15 mm of rainfall and 52% relative humidity across the period.
October is one of the warmer months of the year in Fullerton. Across 45 years of records, the warmest October in Fullerton was 2020 — when the month averaged 23°C — while the coldest was 1981 at 17.9°C. Typical October days reach 26.1°C with nights near 14.4°C. The long-term trend is warming, about 0.4°C per decade.
October is one of the drier months in Fullerton, averaging 15 mm of rainfall. The wettest October on record was 2004 with 131 mm, while the driest were 1988, 1990 and 2019 at 0 mm.
Relative humidity in Fullerton during October averages 52%. The most humid October was 2000 at 66%, and the least humid were 1999 and 2008 at 37%.
October receives about 4.5 kWh/m²/day of solar energy in Fullerton. The sunniest October was 2019 at 5.3 kWh/m²/day, and the cloudiest was 2010 at 3.8.
Average wind speed in Fullerton during October is 1.9 m/s. The windiest October was 1984 at 2.6 m/s, while the calmest were 2001 and 2024 at 1.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 19.6°C | 20.4°C | 19.7°C | 20.8°C | 21.3°C | +1.7°C |
| Avg High | 25.5°C | 26.4°C | 25.3°C | 26.7°C | 27.0°C | +1.5°C |
| Avg Low | 13.7°C | 14.4°C | 14.0°C | 15.0°C | 15.4°C | +1.7°C |
| Avg Rain | 17 mm | 10 mm | 24 mm | 12 mm | 11 mm | -7 mm |
October temperatures in Fullerton have risen by about 1.7°C between 1981–1985 and 2021–2025.
October has ranged from a record low of 6.6°C (1991) to a record high of 37.7°C (2012).
Rainfall in October is one of the drier months, averaging 15 mm, with a wettest year of 131 mm.
One of the best times to visit Fullerton
October is one of the best times to visit Fullerton. Expect days averaging 26.1°C and nights around 14.4°C (mean 20.3°C) — warmer than Fullerton's yearly average — with low rainfall (15 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 25.9°C | 20.2°C | 14.5°C | 32.6°C | 10.3°C | 36 mm | 61% | 1.8 m/s | 4.7 |
| 2024 | 28.3°C | 22.5°C | 16.6°C | 35.0°C | 9.8°C | 0 mm | 47% | 1.5 m/s | 4.6 |
| 2023 | 27.4°C | 21.6°C | 15.7°C | 34.3°C | 11.1°C | 1 mm | 51% | 1.8 m/s | 4.8 |
| 2022 | 26.9°C | 21.2°C | 15.6°C | 31.8°C | 10.6°C | 6 mm | 58% | 1.6 m/s | 4.3 |
| 2021 | 24.7°C | 19.0°C | 13.3°C | 33.1°C | 8.0°C | 21 mm | 55% | 1.9 m/s | 4.6 |
| 2020 🔥 | 29.0°C | 23.0°C | 17.0°C | 37.7°C | 10.6°C | 0 mm | 47% | 1.7 m/s | 4.8 |
| 2019 | 27.3°C | 20.8°C | 14.3°C | 33.6°C | 9.3°C | 0 mm | 42% | 2.1 m/s | 5.3 |
| 2018 | 26.0°C | 20.4°C | 14.9°C | 30.5°C | 11.5°C | 17 mm | 56% | 1.8 m/s | 4.7 |
| 2017 | 28.9°C | 22.3°C | 15.6°C | 37.2°C | 10.8°C | 1 mm | 44% | 1.9 m/s | 4.9 |
| 2016 | 26.0°C | 20.6°C | 15.2°C | 33.3°C | 11.5°C | 14 mm | 55% | 1.8 m/s | 4.5 |
| 2015 | 28.2°C | 22.9°C | 17.6°C | 36.6°C | 13.9°C | 11 mm | 57% | 1.8 m/s | 4.5 |
| 2014 | 28.5°C | 22.4°C | 16.3°C | 35.7°C | 10.9°C | 3 mm | 51% | 1.6 m/s | 4.9 |
| 2013 | 24.7°C | 18.7°C | 12.6°C | 31.0°C | 8.1°C | 7 mm | 51% | 1.9 m/s | 4.7 |
| 2012 | 27.0°C | 21.2°C | 15.3°C | 37.7°C | 9.9°C | 5 mm | 51% | 1.9 m/s | 4.8 |
| 2011 | 26.2°C | 20.0°C | 13.9°C | 35.4°C | 8.2°C | 23 mm | 50% | 1.8 m/s | 4.5 |
| 2010 | 23.8°C | 18.9°C | 14.0°C | 32.7°C | 9.3°C | 41 mm | 64% | 2 m/s | 3.8 |
| 2009 | 24.9°C | 19.0°C | 13.1°C | 34.3°C | 6.6°C | 27 mm | 54% | 2.2 m/s | 4.7 |
| 2008 | 28.4°C | 21.9°C | 15.5°C | 34.4°C | 7.6°C | 1 mm | 37% | 2 m/s | 5 |
| 2007 | 25.7°C | 19.7°C | 13.7°C | 33.2°C | 8.3°C | 9 mm | 49% | 2.2 m/s | 4.8 |
| 2006 | 24.5°C | 18.9°C | 13.3°C | 30.1°C | 10.3°C | 2 mm | 55% | 1.9 m/s | 4.6 |
| 2005 | 25.0°C | 19.3°C | 13.5°C | 33.4°C | 10.1°C | 32 mm | 56% | 1.8 m/s | 4.4 |
| 2004 🌧️ | 23.4°C | 18.3°C | 13.2°C | 31.9°C | 7.9°C | 131 mm | 64% | 1.9 m/s | 4.4 |
| 2003 | 28.7°C | 22.6°C | 16.6°C | 36.0°C | 10.3°C | 6 mm | 46% | 1.7 m/s | 4.5 |
| 2002 | 23.2°C | 18.1°C | 13.0°C | 33.8°C | 10.4°C | 1 mm | 63% | 1.6 m/s | 4 |
| 2001 | 26.4°C | 20.7°C | 15.0°C | 33.3°C | 12.0°C | 3 mm | 55% | 1.5 m/s | 4.4 |
| 2000 | 23.0°C | 18.0°C | 13.0°C | 29.1°C | 7.2°C | 28 mm | 66% | 2 m/s | 4 |
| 1999 | 29.1°C | 22.6°C | 16.1°C | 34.2°C | 11.3°C | 0 mm | 37% | 1.9 m/s | 5.1 |
| 1998 | 25.1°C | 19.2°C | 13.2°C | 30.2°C | 9.5°C | 2 mm | 50% | 1.9 m/s | 4.7 |
| 1997 | 25.9°C | 19.8°C | 13.7°C | 33.2°C | 9.4°C | 2 mm | 52% | 2.3 m/s | 4.7 |
| 1996 | 25.0°C | 19.1°C | 13.3°C | 34.1°C | 7.4°C | 32 mm | 47% | 2.2 m/s | 4.4 |
| 1995 | 26.8°C | 20.7°C | 14.6°C | 33.4°C | 11.2°C | 1 mm | 49% | 1.8 m/s | 4.5 |
| 1994 | 24.7°C | 18.9°C | 13.1°C | 31.8°C | 9.0°C | 16 mm | 52% | 1.9 m/s | 4.6 |
| 1993 | 26.2°C | 20.3°C | 14.3°C | 34.1°C | 9.8°C | 6 mm | 51% | 2 m/s | 4.4 |
| 1992 | 26.1°C | 20.6°C | 15.0°C | 32.8°C | 10.1°C | 30 mm | 58% | 1.8 m/s | 4.2 |
| 1991 | 27.4°C | 21.6°C | 15.8°C | 36.9°C | 6.6°C | 11 mm | 46% | 2 m/s | 4.5 |
| 1990 | 27.9°C | 21.5°C | 15.1°C | 32.5°C | 12.5°C | 0 mm | 42% | 2 m/s | 4.7 |
| 1989 | 25.1°C | 19.1°C | 13.1°C | 32.2°C | 7.1°C | 13 mm | 52% | 2 m/s | 4.5 |
| 1988 | 27.2°C | 21.2°C | 15.1°C | 34.6°C | 11.0°C | 0 mm | 51% | 1.7 m/s | 4.4 |
| 1987 | 26.5°C | 21.2°C | 16.0°C | 37.1°C | 11.8°C | 82 mm | 60% | 1.6 m/s | 3.9 |
| 1986 | 25.1°C | 19.2°C | 13.2°C | 29.6°C | 8.4°C | 7 mm | 50% | 1.9 m/s | 4.3 |
| 1985 | 25.8°C | 19.8°C | 13.7°C | 34.5°C | 8.3°C | 10 mm | 50% | 2.2 m/s | 4.5 |
| 1984 | 24.5°C | 18.3°C | 12.2°C | 30.6°C | 8.0°C | 5 mm | 48% | 2.6 m/s | 4.4 |
| 1983 | 25.8°C | 20.3°C | 14.8°C | 31.8°C | 11.3°C | 27 mm | 59% | 2.1 m/s | — |
| 1982 | 26.0°C | 19.7°C | 13.4°C | 30.2°C | 8.2°C | 8 mm | 42% | 2.4 m/s | — |
| 1981 ❄️ | 23.9°C | 17.9°C | 11.8°C | 30.5°C | 7.9°C | 6 mm | 51% | 2.5 m/s | — |
Actual recorded October data for each year, 1981–2025 — sourced from NASA POWER.
The average high in October is around 26.1°C with lows near 14.4°C (mean 20.3°C), based on 45 years of NASA POWER data.
October averages 15 mm of rainfall in Fullerton, one of the drier months. The wettest on record was 131 mm in 2004.
The hottest October reached 37.7°C in 2012. The coldest dipped to 6.6°C in 1991.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average October temperatures have risen by about 1.7°C. Daytime highs moved from 25.2°C to 26.6°C and overnight lows from 13.2°C to 15.1°C over the same span.
October is one of the warmer months of the year in Fullerton and one of the drier months, so plan for around 26.1°C daytime highs and 14.4°C at night.
Not quite — October is the 8th coolest month in Fullerton, averaging 20.3°C.
For October in Fullerton, pack light layers you can adjust through the day, with typical highs of 26.1°C and lows of 14.4°C.
Relative humidity in October averages 52% — relatively dry.
Average wind speed in October is 1.9 m/s. The windiest October on record averaged 2.6 m/s (1984).
The wettest October on record was 2004 with 131 mm. On average, October sees 15 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 October, 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 October specifically, along with year-by-year records and how the month has changed over the decades.
