December is one of the cooler months of the year in Portland, with average highs near 3.8°C and lows around -0.9°C (mean 1.5°C). It is a relatively wet time of year, averaging 124 mm of rainfall and 83% relative humidity across the period.
December is one of the cooler months of the year in Portland. Across 45 years of records, the warmest December in Portland was 2015 — when the month averaged 5.6°C — while the coldest was 1989 at -6.1°C. Typical December days reach 3.8°C with nights near -0.9°C. The long-term trend is warming, about 0.6°C per decade.
December is a relatively wet time of year in Portland, averaging 124 mm of rainfall. The wettest December on record was 2019 with 215 mm, while the driest were 1982 and 1988 at 38 mm.
Relative humidity in Portland during December averages 83%. The most humid December was 1989 at 90%, and the least humid was 1999 at 79%.
December receives about 1.4 kWh/m²/day of solar energy in Portland. The sunniest Decembers were 1989 and 2018 at 1.7 kWh/m²/day, and the cloudiest was 2013 at 1.1.
Average wind speed in Portland during December is 4.9 m/s. The windiest Decembers were 2009 and 2025 at 5.7 m/s, while the calmest was 2015 at 3.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 0.0°C | 1.4°C | 1.4°C | 2.1°C | 2.7°C | +2.7°C |
| Avg High | 2.5°C | 3.8°C | 3.7°C | 4.4°C | 4.8°C | +2.3°C |
| Avg Low | -2.5°C | -1.0°C | -1.0°C | -0.1°C | 0.5°C | +3°C |
| Avg Rain | 96 mm | 107 mm | 124 mm | 157 mm | 143 mm | +47 mm |
December temperatures in Portland have risen by about 1.8°C between 1981–1985 and 2021–2025.
December has ranged from a record low of -16.6°C (1983) to a record high of 14.5°C (2009).
Rainfall in December is a relatively wet time of year, averaging 124 mm, with a wettest year of 215 mm.
A quieter season to visit Portland
If your dates are flexible, the more temperate months of August and July tend to be the most comfortable for visiting Portland. That said, December — with days averaging 3.8°C and nights around -0.9°C (mean 1.5°C) and higher rainfall (124 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 | 2.9°C | 0.0°C | -2.9°C | 11.6°C | -8.7°C | 90 mm | 81% | 5.7 m/s | — |
| 2024 | 4.2°C | 2.2°C | 0.2°C | 11.9°C | -7.8°C | 155 mm | 82% | 4.7 m/s | 1.5 |
| 2023 | 5.7°C | 3.9°C | 2.1°C | 12.8°C | -4.0°C | 207 mm | 84% | 4.3 m/s | 1.3 |
| 2022 | 5.0°C | 3.1°C | 1.2°C | 12.3°C | -5.7°C | 162 mm | 82% | 5.6 m/s | 1.5 |
| 2021 | 6.2°C | 3.9°C | 1.7°C | 12.3°C | -4.3°C | 105 mm | 80% | 4.7 m/s | 1.3 |
| 2020 | 4.7°C | 2.8°C | 0.8°C | 13.0°C | -6.9°C | 139 mm | 83% | 5.2 m/s | 1.3 |
| 2019 🌧️ | 4.0°C | 1.8°C | -0.4°C | 10.7°C | -9.0°C | 215 mm | 83% | 5.1 m/s | 1.3 |
| 2018 | 3.4°C | 1.2°C | -1.0°C | 10.6°C | -6.2°C | 137 mm | 80% | 4.5 m/s | 1.7 |
| 2017 | 1.6°C | -0.6°C | -2.8°C | 11.6°C | -14.6°C | 143 mm | 84% | 5 m/s | 1.4 |
| 2016 | 4.5°C | 1.9°C | -0.8°C | 10.9°C | -14.0°C | 184 mm | 82% | 5.3 m/s | 1.5 |
| 2015 🔥 | 7.6°C | 5.6°C | 3.6°C | 12.9°C | -3.1°C | 193 mm | 86% | 3.8 m/s | 1.3 |
| 2014 | 5.2°C | 3.1°C | 1.0°C | 10.9°C | -6.3°C | 169 mm | 85% | 4.7 m/s | 1.3 |
| 2013 | 2.5°C | 0.1°C | -2.2°C | 8.2°C | -11.5°C | 123 mm | 88% | 4.6 m/s | 1.1 |
| 2012 | 5.7°C | 3.5°C | 1.2°C | 11.1°C | -6.7°C | 169 mm | 83% | 5.1 m/s | 1.3 |
| 2011 | 6.1°C | 3.7°C | 1.3°C | 11.2°C | -5.2°C | 96 mm | 82% | 4.7 m/s | 1.5 |
| 2010 | 3.1°C | 1.1°C | -1.0°C | 12.1°C | -8.0°C | 139 mm | 82% | 5.6 m/s | 1.4 |
| 2009 | 3.0°C | 0.8°C | -1.5°C | 14.5°C | -10.3°C | 151 mm | 85% | 5.7 m/s | 1.4 |
| 2008 | 4.4°C | 1.3°C | -1.7°C | 11.1°C | -10.0°C | 128 mm | 84% | 5.4 m/s | 1.2 |
| 2007 | 2.6°C | 0.3°C | -2.0°C | 9.7°C | -7.9°C | 145 mm | 84% | 4.8 m/s | 1.3 |
| 2006 | 6.3°C | 4.2°C | 2.1°C | 13.9°C | -3.4°C | 101 mm | 81% | 4.7 m/s | 1.4 |
| 2005 | 2.8°C | 0.9°C | -1.0°C | 8.1°C | -7.0°C | 118 mm | 82% | 4.9 m/s | 1.5 |
| 2004 | 3.7°C | 0.9°C | -2.0°C | 11.3°C | -13.5°C | 127 mm | 83% | 4.9 m/s | 1.3 |
| 2003 | 3.8°C | 1.4°C | -0.9°C | 9.5°C | -7.7°C | 144 mm | 83% | 5.3 m/s | 1.4 |
| 2002 | 2.8°C | 0.6°C | -1.7°C | 10.3°C | -10.3°C | 123 mm | 82% | 5.1 m/s | 1.5 |
| 2001 | 5.6°C | 3.8°C | 2.0°C | 13.0°C | -1.9°C | 77 mm | 82% | 4.2 m/s | 1.5 |
| 2000 | 2.0°C | -0.6°C | -3.3°C | 12.4°C | -11.0°C | 124 mm | 80% | 5.2 m/s | 1.5 |
| 1999 | 4.2°C | 2.0°C | -0.2°C | 9.6°C | -8.4°C | 62 mm | 79% | 4.7 m/s | 1.4 |
| 1998 | 5.0°C | 2.6°C | 0.1°C | 13.2°C | -11.7°C | 44 mm | 81% | 4.4 m/s | 1.4 |
| 1997 | 3.3°C | 1.0°C | -1.4°C | 6.4°C | -10.6°C | 71 mm | 81% | 4.6 m/s | 1.4 |
| 1996 | 5.0°C | 3.1°C | 1.1°C | 10.6°C | -12.1°C | 175 mm | 84% | 4.6 m/s | 1.2 |
| 1995 | 1.4°C | -1.1°C | -3.6°C | 8.0°C | -8.3°C | 95 mm | 87% | 5.4 m/s | 1.5 |
| 1994 | 4.3°C | 2.0°C | -0.4°C | 10.3°C | -10.4°C | 136 mm | 84% | 4.8 m/s | 1.3 |
| 1993 | 3.0°C | 0.7°C | -1.6°C | 9.3°C | -14.8°C | 143 mm | 84% | 4.9 m/s | 1.3 |
| 1992 | 3.6°C | 1.2°C | -1.2°C | 8.1°C | -10.5°C | 62 mm | 82% | 5.3 m/s | 1.2 |
| 1991 | 3.0°C | 0.2°C | -2.6°C | 11.0°C | -9.7°C | 104 mm | 86% | 4.8 m/s | 1.4 |
| 1990 | 4.8°C | 2.3°C | -0.3°C | 11.5°C | -6.5°C | 181 mm | 83% | 4.9 m/s | 1.3 |
| 1989 ❄️ | -3.2°C | -6.1°C | -9.0°C | 5.6°C | -15.3°C | 68 mm | 90% | 5.5 m/s | 1.7 |
| 1988 | 2.3°C | -0.5°C | -3.2°C | 7.3°C | -11.5°C | 38 mm | 81% | 5.1 m/s | 1.5 |
| 1987 | 2.9°C | 0.8°C | -1.2°C | 7.5°C | -13.8°C | 61 mm | 84% | 4.8 m/s | 1.4 |
| 1986 | 3.7°C | 1.3°C | -1.0°C | 11.3°C | -7.8°C | 156 mm | 79% | 5 m/s | 1.4 |
| 1985 | 2.1°C | -0.6°C | -3.2°C | 10.7°C | -13.1°C | 58 mm | 81% | 5.1 m/s | 1.4 |
| 1984 | 5.3°C | 2.8°C | 0.3°C | 9.3°C | -10.0°C | 104 mm | 82% | 4.9 m/s | 1.3 |
| 1983 | 2.4°C | -0.5°C | -3.5°C | 9.9°C | -16.6°C | 207 mm | 86% | 5.3 m/s | — |
| 1982 | 5.1°C | 2.6°C | 0.0°C | 12.8°C | -10.1°C | 38 mm | 84% | 4.7 m/s | — |
| 1981 | 1.7°C | -0.1°C | -1.9°C | 8.0°C | -10.2°C | 133 mm | 88% | 4.8 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 3.8°C with lows near -0.9°C (mean 1.5°C), based on 45 years of NASA POWER data.
December averages 124 mm of rainfall in Portland, a relatively wet time of year. The wettest on record was 215 mm in 2019.
The hottest December reached 14.5°C in 2009. The coldest dipped to -16.6°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 1.8°C. Daytime highs moved from 3.3°C to 4.8°C and overnight lows from -1.7°C to 0.5°C over the same span.
December is one of the cooler months of the year in Portland and a relatively wet time of year, so plan for around 3.8°C daytime highs and -0.9°C at night.
Not quite — December is the 4th coolest month in Portland, averaging 1.5°C.
For December in Portland, pack warm layers and a jacket for chilly mornings, with typical highs of 3.8°C and lows of -0.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in December averages 83% — quite humid.
Average wind speed in December is 4.9 m/s. The windiest December on record averaged 5.7 m/s (2009).
The wettest December on record was 2019 with 215 mm. On average, December sees 124 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 December, 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 December specifically, along with year-by-year records and how the month has changed over the decades.
