August is one of the cooler months of the year in Portland, with average highs near 13.4°C and lows around 10.2°C (mean 11.8°C). It is a relatively wet time of year, averaging 91 mm of rainfall and 79% relative humidity across the period.
August is one of the cooler months of the year in Portland. Across 45 years of records, the warmest August in Portland was 2024 — when the month averaged 13.8°C — while the coldest was 1989 at 10.6°C. Typical August days reach 13.4°C with nights near 10.2°C. The long-term trend is warming, about 0.2°C per decade.
August is a relatively wet time of year in Portland, averaging 91 mm of rainfall. The wettest August on record was 2013 with 209 mm, while the driest was 1982 at 20 mm.
Relative humidity in Portland during August averages 79%. The most humid August was 2011 at 82%, and the least humid was 2025 at 76%.
August receives about 2.8 kWh/m²/day of solar energy in Portland. The sunniest August was 2025 at 3.1 kWh/m²/day, and the cloudiest were 2008, 2010 and 2013 at 2.5.
Average wind speed in Portland during August is 6.2 m/s. The windiest August was 1991 at 8.1 m/s, while the calmest were 1982 and 2014 at 4.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 11.5°C | 11.6°C | 11.9°C | 11.8°C | 12.5°C | +1°C |
| Avg High | 13.1°C | 13.2°C | 13.5°C | 13.2°C | 14.1°C | +1°C |
| Avg Low | 9.9°C | 9.9°C | 10.3°C | 10.3°C | 10.8°C | +0.9°C |
| Avg Rain | 95 mm | 101 mm | 97 mm | 93 mm | 57 mm | -37 mm |
August temperatures in Portland have risen by about 1°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 5.3°C (1995) to a record high of 19.7°C (2005).
Rainfall in August is a relatively wet time of year, averaging 91 mm, with a wettest year of 209 mm.
A quieter season to visit Portland
If your dates are flexible, the more temperate months of February and January tend to be the most comfortable for visiting Portland. That said, August — with days averaging 13.4°C and nights around 10.2°C (mean 11.8°C) and higher rainfall (91 mm) — can still be rewarding for travellers who don't mind the cooler conditions, and often means fewer crowds.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 14.0°C | 12.3°C | 10.6°C | 16.9°C | 8.4°C | 62 mm | 76% | 5.6 m/s | 3.1 |
| 2024 🔥 | 15.7°C | 13.8°C | 11.9°C | 19.0°C | 9.3°C | 40 mm | 77% | 6.5 m/s | 2.8 |
| 2023 | 14.1°C | 12.6°C | 11.1°C | 18.8°C | 9.0°C | 35 mm | 78% | 5.2 m/s | 2.9 |
| 2022 | 13.7°C | 12.2°C | 10.7°C | 17.7°C | 8.5°C | 87 mm | 79% | 6 m/s | 2.7 |
| 2021 | 13.8°C | 12.3°C | 10.7°C | 16.8°C | 8.7°C | 54 mm | 80% | 6.6 m/s | 2.9 |
| 2020 | 13.0°C | 11.5°C | 10.0°C | 17.8°C | 8.5°C | 65 mm | 79% | 6.4 m/s | 2.9 |
| 2019 | 12.8°C | 11.2°C | 9.7°C | 16.6°C | 7.5°C | 57 mm | 78% | 6.2 m/s | 2.8 |
| 2018 | 13.2°C | 11.7°C | 10.1°C | 16.7°C | 7.9°C | 77 mm | 77% | 6.9 m/s | 2.7 |
| 2017 | 13.1°C | 11.8°C | 10.4°C | 17.1°C | 8.4°C | 75 mm | 77% | 6.2 m/s | 2.8 |
| 2016 | 13.5°C | 11.9°C | 10.3°C | 19.2°C | 8.7°C | 66 mm | 78% | 5.8 m/s | 2.7 |
| 2015 | 12.2°C | 11.0°C | 9.8°C | 16.7°C | 8.6°C | 33 mm | 79% | 5.9 m/s | 2.8 |
| 2014 | 13.4°C | 12.0°C | 10.5°C | 17.7°C | 8.4°C | 39 mm | 77% | 4.6 m/s | 2.7 |
| 2013 🌧️ | 14.0°C | 12.5°C | 10.9°C | 17.7°C | 8.7°C | 209 mm | 81% | 7.7 m/s | 2.5 |
| 2012 | 12.9°C | 11.4°C | 9.9°C | 16.1°C | 8.5°C | 104 mm | 79% | 7.2 m/s | 2.7 |
| 2011 | 14.4°C | 12.7°C | 11.0°C | 18.2°C | 9.1°C | 83 mm | 82% | 5.3 m/s | 2.9 |
| 2010 | 12.6°C | 11.3°C | 10.1°C | 15.0°C | 8.7°C | 181 mm | 79% | 7.2 m/s | 2.5 |
| 2009 | 14.1°C | 12.5°C | 10.9°C | 18.3°C | 8.6°C | 118 mm | 80% | 7.4 m/s | 2.7 |
| 2008 | 12.3°C | 11.2°C | 10.0°C | 15.1°C | 8.5°C | 129 mm | 79% | 6 m/s | 2.5 |
| 2007 | 14.0°C | 12.3°C | 10.6°C | 19.1°C | 8.2°C | 81 mm | 79% | 6.3 m/s | 2.9 |
| 2006 | 13.9°C | 12.1°C | 10.3°C | 17.9°C | 8.0°C | 45 mm | 77% | 5.2 m/s | 2.9 |
| 2005 | 14.0°C | 12.2°C | 10.5°C | 19.7°C | 8.3°C | 93 mm | 77% | 6.7 m/s | 2.6 |
| 2004 | 13.2°C | 11.7°C | 10.2°C | 17.3°C | 8.6°C | 109 mm | 79% | 5.9 m/s | 2.7 |
| 2003 | 12.8°C | 11.2°C | 9.5°C | 15.6°C | 7.7°C | 99 mm | 78% | 6.9 m/s | 2.6 |
| 2002 | 13.2°C | 11.7°C | 10.1°C | 16.9°C | 8.0°C | 58 mm | 76% | 5.5 m/s | 2.8 |
| 2001 | 13.9°C | 12.3°C | 10.7°C | 17.6°C | 8.9°C | 158 mm | 77% | 6.9 m/s | 2.6 |
| 2000 | 13.4°C | 11.7°C | 10.1°C | 17.0°C | 8.9°C | 79 mm | 79% | 5.1 m/s | 2.8 |
| 1999 | 14.2°C | 12.5°C | 10.9°C | 19.1°C | 9.1°C | 73 mm | 78% | 5.2 m/s | 2.7 |
| 1998 | 13.6°C | 11.9°C | 10.3°C | 16.4°C | 8.6°C | 43 mm | 81% | 5 m/s | 3 |
| 1997 | 13.0°C | 11.4°C | 9.8°C | 16.5°C | 7.2°C | 89 mm | 77% | 6.2 m/s | 2.6 |
| 1996 | 12.8°C | 11.4°C | 10.0°C | 15.5°C | 8.2°C | 129 mm | 80% | 6.5 m/s | 2.8 |
| 1995 | 13.7°C | 11.6°C | 9.4°C | 18.6°C | 5.3°C | 75 mm | 80% | 6.4 m/s | 3 |
| 1994 | 12.3°C | 11.0°C | 9.6°C | 17.9°C | 7.6°C | 60 mm | 77% | 6.1 m/s | 2.9 |
| 1993 | 14.6°C | 12.6°C | 10.6°C | 17.9°C | 8.2°C | 89 mm | 79% | 6.4 m/s | 3 |
| 1992 | 12.6°C | 11.0°C | 9.4°C | 16.8°C | 7.9°C | 143 mm | 79% | 6.8 m/s | 2.6 |
| 1991 | 13.0°C | 11.4°C | 9.8°C | 16.1°C | 7.5°C | 160 mm | 78% | 8.1 m/s | 2.6 |
| 1990 | 12.2°C | 10.9°C | 9.5°C | 15.3°C | 7.5°C | 152 mm | 80% | 6.6 m/s | 2.7 |
| 1989 ❄️ | 12.0°C | 10.6°C | 9.3°C | 14.2°C | 7.3°C | 134 mm | 80% | 5.8 m/s | 2.7 |
| 1988 | 13.6°C | 12.0°C | 10.5°C | 17.2°C | 9.0°C | 87 mm | 79% | 6.1 m/s | 2.8 |
| 1987 | 12.9°C | 11.4°C | 9.8°C | 16.2°C | 7.5°C | 63 mm | 80% | 5.3 m/s | 2.8 |
| 1986 | 13.1°C | 11.3°C | 9.5°C | 17.4°C | 7.6°C | 95 mm | 81% | 5.9 m/s | 3 |
| 1985 | 12.9°C | 11.3°C | 9.6°C | 16.7°C | 7.8°C | 88 mm | 80% | 6 m/s | 2.7 |
| 1984 | 13.0°C | 11.5°C | 10.1°C | 15.5°C | 7.5°C | 115 mm | 81% | 6.9 m/s | 2.8 |
| 1983 | 13.6°C | 12.0°C | 10.4°C | 16.5°C | 8.2°C | 92 mm | 80% | 5.9 m/s | — |
| 1982 | 14.2°C | 12.0°C | 9.9°C | 18.1°C | 7.7°C | 20 mm | 78% | 4.6 m/s | — |
| 1981 | 12.7°C | 11.2°C | 9.7°C | 15.5°C | 7.6°C | 157 mm | 80% | 6.9 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 13.4°C with lows near 10.2°C (mean 11.8°C), based on 45 years of NASA POWER data.
August averages 91 mm of rainfall in Portland, a relatively wet time of year. The wettest on record was 209 mm in 2013.
The hottest August reached 19.7°C in 2005. The coldest dipped to 5.3°C in 1995.
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 13.3°C to 14.3°C and overnight lows from 9.9°C to 11°C over the same span.
August is one of the cooler months of the year in Portland and a relatively wet time of year, so plan for around 13.4°C daytime highs and 10.2°C at night.
Not quite — August is the 2nd coolest month in Portland, averaging 11.8°C.
For August in Portland, pack light layers you can adjust through the day, with typical highs of 13.4°C and lows of 10.2°C. Bring an umbrella or light rain jacket too.
Relative humidity in August averages 79% — quite humid.
Average wind speed in August is 6.2 m/s. The windiest August on record averaged 8.1 m/s (1991).
The wettest August on record was 2013 with 209 mm. On average, August sees 91 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 Portland 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.
