August is one of the warmer months of the year in San Mateo, with average highs near 18.4°C and lows around 13.5°C (mean 16°C). It is one of the drier months, averaging 3 mm of rainfall and 86% relative humidity across the period.
August is one of the warmer months of the year in San Mateo. Across 45 years of records, the warmest August in San Mateo was 2015 — when the month averaged 17.9°C — while the coldest were 2000 and 2011 at 14.6°C. Typical August days reach 18.4°C with nights near 13.5°C. The long-term August temperature trend is broadly flat.
August is one of the drier months in San Mateo, averaging 3 mm of rainfall. The wettest August on record was 1997 with 12 mm, while the driest were 1998, 2021 and 2022 at 0 mm.
Relative humidity in San Mateo during August averages 86%. The most humid August was 2011 at 88%, and the least humid was 1985 at 82%.
August receives about 5.9 kWh/m²/day of solar energy in San Mateo. The sunniest Augusts were 2019, 2022 and 2025, among others at 6.4 kWh/m²/day, and the cloudiest was 1986 at 4.4.
Average wind speed in San Mateo during August is 3.3 m/s. The windiest August was 1984 at 3.9 m/s, while the calmest were 1987 and 2005 at 2.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 15.8°C | 16.0°C | 15.6°C | 16.0°C | 16.4°C | +0.6°C |
| Avg High | 18.5°C | 18.6°C | 18.0°C | 18.2°C | 18.8°C | +0.3°C |
| Avg Low | 13.2°C | 13.4°C | 13.3°C | 13.8°C | 14.1°C | +0.9°C |
| Avg Rain | 4 mm | 4 mm | 4 mm | 2 mm | 1 mm | -3 mm |
August temperatures in San Mateo have risen by about 0.4°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 10.7°C (1996) to a record high of 29.6°C (2020).
Rainfall in August is one of the drier months, averaging 3 mm, with a wettest year of 12 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0°C per decade while lows rose 0.2°C per decade, narrowing the gap between day and night.
One of the best times to visit San Mateo
August is one of the best times to visit San Mateo. Expect days averaging 18.4°C and nights around 13.5°C (mean 16°C) — warmer than San Mateo's yearly average — with low rainfall (3 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 | 18.8°C | 16.5°C | 14.3°C | 22.5°C | 13.3°C | 2 mm | 86% | 3.7 m/s | 6.4 |
| 2024 | 18.5°C | 16.2°C | 13.9°C | 23.0°C | 12.8°C | 1 mm | 86% | 3.5 m/s | 6.3 |
| 2023 | 19.5°C | 17.0°C | 14.5°C | 25.3°C | 13.1°C | 1 mm | 86% | 3.4 m/s | 5.9 |
| 2022 | 18.5°C | 16.3°C | 14.1°C | 21.1°C | 12.7°C | 0 mm | 86% | 3.2 m/s | 6.4 |
| 2021 | 18.4°C | 16.0°C | 13.7°C | 24.1°C | 12.0°C | 0 mm | 86% | 3.3 m/s | 5.6 |
| 2020 | 19.1°C | 16.6°C | 14.1°C | 29.6°C | 12.4°C | 2 mm | 84% | 3.2 m/s | 5.6 |
| 2019 | 19.7°C | 17.2°C | 14.7°C | 24.1°C | 13.1°C | 2 mm | 86% | 3.4 m/s | 6.4 |
| 2018 | 17.6°C | 15.5°C | 13.4°C | 19.3°C | 12.1°C | 1 mm | 87% | 3.3 m/s | 5.5 |
| 2017 | 19.0°C | 16.7°C | 14.4°C | 28.5°C | 12.9°C | 1 mm | 84% | 3.1 m/s | 5.3 |
| 2016 | 17.3°C | 15.3°C | 13.3°C | 18.3°C | 12.0°C | 1 mm | 87% | 3.3 m/s | 5.5 |
| 2015 🔥 | 20.0°C | 17.9°C | 15.7°C | 26.5°C | 14.4°C | 2 mm | 84% | 3.2 m/s | 6.1 |
| 2014 | 19.3°C | 17.1°C | 15.0°C | 22.2°C | 14.2°C | 1 mm | 85% | 3.2 m/s | 5.4 |
| 2013 | 18.1°C | 16.0°C | 14.0°C | 21.5°C | 12.3°C | 3 mm | 87% | 3.2 m/s | 6.1 |
| 2012 | 16.8°C | 14.7°C | 12.6°C | 20.3°C | 11.7°C | 3 mm | 87% | 3.3 m/s | 5.7 |
| 2011 | 16.6°C | 14.6°C | 12.7°C | 19.7°C | 11.8°C | 3 mm | 88% | 3.4 m/s | 5.7 |
| 2010 | 17.2°C | 14.8°C | 12.5°C | 27.5°C | 11.4°C | 1 mm | 85% | 3.4 m/s | 5.6 |
| 2009 | 18.4°C | 15.8°C | 13.3°C | 25.5°C | 12.2°C | 3 mm | 86% | 3 m/s | 6.2 |
| 2008 | 18.3°C | 15.7°C | 13.2°C | 26.3°C | 11.6°C | 1 mm | 86% | 3.3 m/s | 6 |
| 2007 | 17.9°C | 15.8°C | 13.6°C | 23.6°C | 12.0°C | 12 mm | 87% | 3.2 m/s | 6.2 |
| 2006 | 17.8°C | 15.4°C | 13.1°C | 27.3°C | 12.2°C | 2 mm | 86% | 3.1 m/s | 5.8 |
| 2005 | 17.4°C | 15.1°C | 12.9°C | 22.5°C | 11.9°C | 2 mm | 87% | 2.7 m/s | 5.6 |
| 2004 | 19.0°C | 16.6°C | 14.2°C | 27.2°C | 12.4°C | 2 mm | 86% | 3 m/s | 5.7 |
| 2003 | 19.1°C | 16.8°C | 14.5°C | 22.6°C | 12.8°C | 4 mm | 86% | 3.2 m/s | 6.4 |
| 2002 | 18.2°C | 15.5°C | 12.7°C | 25.4°C | 11.6°C | 2 mm | 84% | 3.2 m/s | 5.5 |
| 2001 | 17.2°C | 15.0°C | 12.9°C | 18.8°C | 11.6°C | 1 mm | 88% | 3.4 m/s | 6.3 |
| 2000 ❄️ | 16.9°C | 14.6°C | 12.3°C | 18.6°C | 11.4°C | 8 mm | 87% | 3.2 m/s | 6.2 |
| 1999 | 18.0°C | 15.6°C | 13.2°C | 22.0°C | 11.5°C | 3 mm | 86% | 3.5 m/s | 5.9 |
| 1998 | 18.6°C | 16.0°C | 13.3°C | 24.7°C | 12.0°C | 0 mm | 85% | 3.3 m/s | 5.7 |
| 1997 🌧️ | 19.6°C | 17.3°C | 15.0°C | 21.5°C | 13.1°C | 12 mm | 84% | 3.4 m/s | 6.4 |
| 1996 | 17.8°C | 15.0°C | 12.3°C | 21.6°C | 10.7°C | 3 mm | 86% | 3.3 m/s | 6.1 |
| 1995 | 18.2°C | 15.4°C | 12.7°C | 23.2°C | 11.5°C | 2 mm | 84% | 3.4 m/s | 6.2 |
| 1994 | 18.0°C | 15.4°C | 12.8°C | 20.6°C | 11.7°C | 3 mm | 87% | 3.7 m/s | 6.3 |
| 1993 | 19.7°C | 16.7°C | 13.8°C | 27.6°C | 12.4°C | 4 mm | 82% | 3.5 m/s | 5.8 |
| 1992 | 18.4°C | 15.8°C | 13.2°C | 22.5°C | 12.0°C | 2 mm | 86% | 3.1 m/s | 5.5 |
| 1991 | 18.3°C | 16.0°C | 13.7°C | 26.6°C | 12.5°C | 7 mm | 87% | 3.4 m/s | 5.6 |
| 1990 | 19.4°C | 16.8°C | 14.2°C | 21.7°C | 12.2°C | 2 mm | 84% | 3.3 m/s | 5.9 |
| 1989 | 18.0°C | 15.3°C | 12.5°C | 22.0°C | 11.7°C | 2 mm | 85% | 3.1 m/s | 5.8 |
| 1988 | 18.4°C | 15.9°C | 13.3°C | 21.9°C | 12.1°C | 1 mm | 84% | 3.3 m/s | 5.6 |
| 1987 | 18.6°C | 15.8°C | 13.1°C | 19.9°C | 11.9°C | 2 mm | 83% | 2.7 m/s | 5.4 |
| 1986 | 17.9°C | 15.4°C | 12.8°C | 19.5°C | 11.7°C | 3 mm | 86% | 2.9 m/s | 4.4 |
| 1985 | 18.6°C | 16.0°C | 13.3°C | 24.6°C | 12.3°C | 3 mm | 82% | 3.5 m/s | 5.9 |
| 1984 | 19.0°C | 16.3°C | 13.5°C | 21.9°C | 12.6°C | 3 mm | 84% | 3.9 m/s | 5.9 |
| 1983 | 19.5°C | 17.0°C | 14.5°C | 21.9°C | 13.2°C | 6 mm | 85% | 3.4 m/s | — |
| 1982 | 18.0°C | 15.3°C | 12.7°C | 22.8°C | 10.9°C | 6 mm | 86% | 3.6 m/s | — |
| 1981 | 18.3°C | 15.5°C | 12.7°C | 20.8°C | 11.9°C | 8 mm | 85% | 3.7 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 18.4°C with lows near 13.5°C (mean 16°C), based on 45 years of NASA POWER data.
August averages 3 mm of rainfall in San Mateo, one of the drier months. The wettest on record was 12 mm in 1997.
The hottest August reached 29.6°C in 2020. The coldest dipped to 10.7°C in 1996.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 0.4°C. Daytime highs moved from 18.7°C to 18.7°C and overnight lows from 13.3°C to 14.1°C over the same span.
August is one of the warmer months of the year in San Mateo and one of the drier months, so plan for around 18.4°C daytime highs and 13.5°C at night.
Not quite — August is the 11th coolest month in San Mateo, averaging 16°C.
For August in San Mateo, pack light layers you can adjust through the day, with typical highs of 18.4°C and lows of 13.5°C.
Relative humidity in August averages 86% — quite humid.
Average wind speed in August is 3.3 m/s. The windiest August on record averaged 3.9 m/s (1984).
The wettest August on record was 1997 with 12 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 San Mateo 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.
