August is one of the warmer months of the year in Simi Valley, with average highs near 34.9°C and lows around 17.7°C (mean 26.3°C). It is one of the drier months, averaging 3 mm of rainfall and 32% relative humidity across the period.
August is one of the warmer months of the year in Simi Valley. Across 45 years of records, the warmest Augusts in Simi Valley were 2012 and 2022 — when the month averaged 28.3°C — while the coldest was 1989 at 23.8°C. Typical August days reach 34.9°C with nights near 17.7°C. The long-term trend is warming, about 0.3°C per decade.
August is one of the drier months in Simi Valley, averaging 3 mm of rainfall. The wettest August on record was 2023 with 61 mm, while the driest were 2016, 2018 and 2019, among others at 0 mm.
Relative humidity in Simi Valley during August averages 32%. The most humid August was 1983 at 43%, and the least humid was 1986 at 22%.
August receives about 7.3 kWh/m²/day of solar energy in Simi Valley. The sunniest Augusts were 2006, 2010 and 2019 at 7.7 kWh/m²/day, and the cloudiest was 1984 at 6.5.
Average wind speed in Simi Valley during August is 1.8 m/s. The windiest Augusts were 1995 and 1997 at 2 m/s, while the calmest were 2007, 2008 and 2012, among others at 1.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 25.7°C | 26.3°C | 26.2°C | 26.4°C | 27.2°C | +1.5°C |
| Avg High | 34.2°C | 35.0°C | 34.9°C | 35.1°C | 35.6°C | +1.4°C |
| Avg Low | 17.3°C | 17.7°C | 17.6°C | 17.7°C | 18.7°C | +1.4°C |
| Avg Rain | 5 mm | 1 mm | 1 mm | 1 mm | 11 mm | +6 mm |
August temperatures in Simi Valley have risen by about 1°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 9.8°C (1990) to a record high of 42.5°C (1997).
Rainfall in August is one of the drier months, averaging 3 mm, with a wettest year of 61 mm.
A good time to visit Simi Valley
August is a good time to visit Simi Valley, with days averaging 34.9°C and nights around 17.7°C (mean 26.3°C, warmer than Simi Valley'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 | 36.2°C | 27.4°C | 18.5°C | 39.7°C | 15.4°C | 0 mm | 30% | 1.8 m/s | 7.3 |
| 2024 | 36.0°C | 27.2°C | 18.4°C | 40.7°C | 12.7°C | 0 mm | 29% | 1.8 m/s | 7.5 |
| 2023 🌧️ | 33.5°C | 25.5°C | 17.4°C | 39.1°C | 14.2°C | 61 mm | 41% | 1.9 m/s | 7.1 |
| 2022 | 36.6°C | 28.3°C | 20.1°C | 42.1°C | 16.0°C | 1 mm | 31% | 1.8 m/s | 7.2 |
| 2021 | 35.1°C | 26.7°C | 18.3°C | 39.3°C | 14.3°C | 0 mm | 34% | 1.8 m/s | 7.2 |
| 2020 | 36.4°C | 27.9°C | 19.4°C | 41.5°C | 13.6°C | 1 mm | 33% | 1.8 m/s | 7.2 |
| 2019 | 35.5°C | 26.6°C | 17.6°C | 38.8°C | 14.0°C | 0 mm | 29% | 1.8 m/s | 7.7 |
| 2018 | 35.9°C | 27.2°C | 18.5°C | 40.6°C | 13.8°C | 0 mm | 34% | 1.8 m/s | 7.4 |
| 2017 | 35.1°C | 27.0°C | 18.9°C | 41.2°C | 13.6°C | 4 mm | 36% | 1.8 m/s | 7.1 |
| 2016 | 35.0°C | 26.2°C | 17.3°C | 39.2°C | 13.5°C | 0 mm | 30% | 1.8 m/s | 7.6 |
| 2015 | 35.6°C | 26.6°C | 17.6°C | 40.6°C | 13.3°C | 0 mm | 35% | 1.8 m/s | 7.4 |
| 2014 | 33.1°C | 25.1°C | 17.1°C | 38.1°C | 13.4°C | 2 mm | 37% | 1.9 m/s | 7.4 |
| 2013 | 33.9°C | 25.5°C | 17.0°C | 37.9°C | 12.7°C | 1 mm | 31% | 1.8 m/s | 7.4 |
| 2012 🔥 | 36.6°C | 28.3°C | 20.0°C | 40.2°C | 13.1°C | 2 mm | 27% | 1.7 m/s | 7.2 |
| 2011 | 35.8°C | 26.4°C | 17.0°C | 40.9°C | 13.5°C | 0 mm | 27% | 1.8 m/s | 7.6 |
| 2010 | 34.0°C | 25.2°C | 16.4°C | 40.5°C | 10.6°C | 0 mm | 30% | 1.8 m/s | 7.7 |
| 2009 | 34.6°C | 25.9°C | 17.2°C | 39.1°C | 12.8°C | 1 mm | 28% | 1.8 m/s | 7.4 |
| 2008 | 35.6°C | 26.9°C | 18.3°C | 39.0°C | 14.7°C | 0 mm | 33% | 1.7 m/s | 7.4 |
| 2007 | 35.8°C | 27.1°C | 18.4°C | 40.3°C | 13.2°C | 0 mm | 32% | 1.7 m/s | 7.4 |
| 2006 | 33.5°C | 24.9°C | 16.4°C | 38.0°C | 12.4°C | 0 mm | 36% | 1.8 m/s | 7.7 |
| 2005 | 34.8°C | 26.4°C | 17.9°C | 40.0°C | 14.2°C | 1 mm | 33% | 1.8 m/s | 7.5 |
| 2004 | 34.1°C | 25.4°C | 16.6°C | 40.8°C | 12.8°C | 0 mm | 35% | 1.8 m/s | 7.6 |
| 2003 | 35.4°C | 27.0°C | 18.5°C | 39.0°C | 14.3°C | 4 mm | 32% | 1.9 m/s | 7.4 |
| 2002 | 34.7°C | 25.6°C | 16.5°C | 40.3°C | 12.6°C | 0 mm | 31% | 1.8 m/s | 7.4 |
| 2001 | 35.3°C | 26.5°C | 17.7°C | 39.6°C | 13.0°C | 0 mm | 32% | 1.9 m/s | 7.6 |
| 2000 | 34.7°C | 26.4°C | 18.1°C | 39.3°C | 13.5°C | 3 mm | 32% | 1.9 m/s | 7.3 |
| 1999 | 33.8°C | 25.2°C | 16.5°C | 40.1°C | 11.9°C | 0 mm | 30% | 1.9 m/s | 7.5 |
| 1998 | 36.8°C | 28.2°C | 19.6°C | 41.4°C | 13.6°C | 4 mm | 31% | 1.8 m/s | 7.3 |
| 1997 | 34.7°C | 25.8°C | 16.9°C | 42.5°C | 12.2°C | 0 mm | 39% | 2 m/s | 7.4 |
| 1996 | 36.7°C | 27.8°C | 18.8°C | 40.9°C | 13.0°C | 1 mm | 28% | 1.8 m/s | 7.6 |
| 1995 | 35.6°C | 27.0°C | 18.4°C | 39.1°C | 13.5°C | 1 mm | 26% | 2 m/s | 7.1 |
| 1994 | 36.3°C | 27.6°C | 19.0°C | 41.2°C | 14.2°C | 0 mm | 29% | 1.8 m/s | 7 |
| 1993 | 33.5°C | 25.0°C | 16.5°C | 39.8°C | 12.2°C | 0 mm | 35% | 1.8 m/s | 7.1 |
| 1992 | 35.4°C | 27.0°C | 18.7°C | 40.0°C | 10.8°C | 0 mm | 32% | 1.8 m/s | 7.3 |
| 1991 | 32.9°C | 24.4°C | 15.8°C | 37.8°C | 11.7°C | 1 mm | 37% | 1.8 m/s | 7 |
| 1990 | 33.9°C | 25.1°C | 16.4°C | 38.7°C | 9.8°C | 2 mm | 35% | 1.8 m/s | 7 |
| 1989 ❄️ | 32.5°C | 23.8°C | 15.2°C | 37.7°C | 11.1°C | 0 mm | 35% | 1.8 m/s | 7.3 |
| 1988 | 33.6°C | 25.3°C | 17.0°C | 37.7°C | 11.6°C | 3 mm | 36% | 1.7 m/s | 6.9 |
| 1987 | 33.5°C | 25.0°C | 16.5°C | 38.7°C | 10.5°C | 0 mm | 34% | 1.9 m/s | 7.1 |
| 1986 | 35.9°C | 27.4°C | 19.0°C | 38.4°C | 15.2°C | 0 mm | 22% | 1.7 m/s | 7.3 |
| 1985 | 34.7°C | 25.5°C | 16.3°C | 41.2°C | 12.7°C | 0 mm | 29% | 1.8 m/s | 7.3 |
| 1984 | 34.2°C | 26.2°C | 18.2°C | 39.9°C | 13.9°C | 3 mm | 38% | 1.9 m/s | 6.5 |
| 1983 | 32.8°C | 25.2°C | 17.7°C | 39.4°C | 10.6°C | 36 mm | 43% | 1.8 m/s | — |
| 1982 | 34.2°C | 26.1°C | 18.0°C | 39.3°C | 12.8°C | 1 mm | 28% | 1.9 m/s | — |
| 1981 | 36.0°C | 26.8°C | 17.7°C | 39.9°C | 13.4°C | 0 mm | 23% | 1.9 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 34.9°C with lows near 17.7°C (mean 26.3°C), based on 45 years of NASA POWER data.
August averages 3 mm of rainfall in Simi Valley, one of the drier months. The wettest on record was 61 mm in 2023.
The hottest August reached 42.5°C in 1997. The coldest dipped to 9.8°C in 1990.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 1°C. Daytime highs moved from 34.4°C to 35.5°C and overnight lows from 17.6°C to 18.5°C over the same span.
August is one of the warmer months of the year in Simi Valley and one of the drier months, so plan for around 34.9°C daytime highs and 17.7°C at night.
Not quite — August is the 12th coolest month in Simi Valley, averaging 26.3°C.
For August in Simi Valley, pack light, breathable clothing and sun protection, with typical highs of 34.9°C and lows of 17.7°C.
Relative humidity in August averages 32% — relatively dry.
Average wind speed in August is 1.8 m/s. The windiest August on record averaged 2 m/s (1995).
The wettest August on record was 2023 with 61 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 Simi Valley 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.
