December is one of the warmer months of the year in Portland, with average highs near 17.9°C and lows around 13.7°C (mean 15.8°C). It is one of the drier months, averaging 49 mm of rainfall and 75% relative humidity across the period.
December is one of the warmer months of the year in Portland. Across 45 years of records, the warmest December in Portland was 2015 — when the month averaged 17.2°C — while the coldest were 1995 and 2001 at 13.9°C. Typical December days reach 17.9°C with nights near 13.7°C. The long-term trend is warming, about 0.2°C per decade.
December is one of the drier months in Portland, averaging 49 mm of rainfall. The wettest December on record was 2010 with 125 mm, while the driest was 2021 at 12 mm.
Relative humidity in Portland during December averages 75%. The most humid December was 1992 at 83%, and the least humid was 2005 at 70%.
December receives about 6.9 kWh/m²/day of solar energy in Portland. The sunniest December was 2000 at 7.9 kWh/m²/day, and the cloudiest was 1992 at 5.9.
Average wind speed in Portland during December is 5.4 m/s. The windiest December was 1984 at 6.5 m/s, while the calmest was 1983 at 4.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 15.7°C | 15.4°C | 15.9°C | 16.3°C | 15.8°C | +0.1°C |
| Avg High | 17.9°C | 17.4°C | 18.1°C | 18.4°C | 17.9°C | 0°C |
| Avg Low | 13.5°C | 13.4°C | 13.7°C | 14.1°C | 13.8°C | +0.3°C |
| Avg Rain | 53 mm | 46 mm | 49 mm | 44 mm | 54 mm | +1 mm |
December temperatures in Portland have stayed relatively stable across the record.
December has ranged from a record low of 9.9°C (1987) to a record high of 32.9°C (2006).
Rainfall in December is one of the drier months, averaging 49 mm, with a wettest year of 125 mm.
One of the best times to visit Portland
December is one of the best times to visit Portland. Expect days averaging 17.9°C and nights around 13.7°C (mean 15.8°C) — warmer than Portland's yearly average — with moderate rainfall (49 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 | 17.8°C | 15.5°C | 13.2°C | 29.7°C | 12.0°C | 33 mm | 72% | 5.5 m/s | — |
| 2024 | 19.4°C | 17.1°C | 14.8°C | 29.6°C | 13.5°C | 52 mm | 74% | 5.2 m/s | 7.2 |
| 2023 | 17.6°C | 16.0°C | 14.3°C | 24.4°C | 13.0°C | 78 mm | 79% | 5.8 m/s | 6.5 |
| 2022 | 18.0°C | 15.7°C | 13.4°C | 30.2°C | 11.2°C | 48 mm | 76% | 5.1 m/s | 7.3 |
| 2021 | 17.4°C | 15.5°C | 13.7°C | 25.4°C | 12.4°C | 12 mm | 74% | 5.1 m/s | 7.8 |
| 2020 | 17.0°C | 15.0°C | 13.1°C | 27.3°C | 11.6°C | 98 mm | 75% | 5.7 m/s | 6.5 |
| 2019 | 17.9°C | 15.7°C | 13.5°C | 32.4°C | 10.9°C | 17 mm | 76% | 5.7 m/s | 7.3 |
| 2018 | 19.2°C | 17.0°C | 14.8°C | 28.8°C | 12.9°C | 56 mm | 76% | 4.9 m/s | 6.8 |
| 2017 | 19.1°C | 17.1°C | 15.1°C | 28.8°C | 12.8°C | 26 mm | 74% | 5.3 m/s | 6.7 |
| 2016 | 18.3°C | 15.9°C | 13.5°C | 25.7°C | 11.3°C | 33 mm | 74% | 4.9 m/s | 6.9 |
| 2015 🔥 | 19.8°C | 17.2°C | 14.5°C | 29.8°C | 11.3°C | 42 mm | 71% | 5.1 m/s | 7.6 |
| 2014 | 17.6°C | 15.9°C | 14.2°C | 24.3°C | 12.6°C | 32 mm | 77% | 5.2 m/s | 6.6 |
| 2013 | 17.5°C | 15.3°C | 13.1°C | 26.6°C | 11.1°C | 42 mm | 78% | 5 m/s | 7.2 |
| 2012 | 18.2°C | 16.1°C | 14.0°C | 27.5°C | 11.9°C | 45 mm | 74% | 5.3 m/s | 7 |
| 2011 | 18.3°C | 16.4°C | 14.4°C | 23.6°C | 12.4°C | 25 mm | 77% | 5.1 m/s | 7.2 |
| 2010 🌧️ | 17.9°C | 15.9°C | 13.8°C | 26.0°C | 11.8°C | 125 mm | 78% | 5.5 m/s | 7.2 |
| 2009 | 18.9°C | 16.5°C | 14.1°C | 28.5°C | 12.6°C | 50 mm | 72% | 4.9 m/s | 7.4 |
| 2008 | 16.5°C | 14.8°C | 13.0°C | 23.8°C | 11.5°C | 109 mm | 77% | 5.7 m/s | 6.7 |
| 2007 | 19.2°C | 16.7°C | 14.3°C | 29.8°C | 12.4°C | 53 mm | 75% | 4.9 m/s | 7 |
| 2006 | 17.8°C | 15.4°C | 13.0°C | 32.9°C | 11.0°C | 14 mm | 70% | 5.1 m/s | 7.5 |
| 2005 | 20.0°C | 17.1°C | 14.3°C | 28.0°C | 12.6°C | 38 mm | 70% | 6.3 m/s | 6.9 |
| 2004 | 18.3°C | 16.2°C | 14.2°C | 27.7°C | 12.4°C | 42 mm | 77% | 5.2 m/s | 7.1 |
| 2003 | 18.8°C | 16.5°C | 14.1°C | 27.7°C | 12.0°C | 38 mm | 74% | 5.2 m/s | 7 |
| 2002 | 17.6°C | 15.5°C | 13.4°C | 28.2°C | 11.2°C | 46 mm | 76% | 5.7 m/s | 6.4 |
| 2001 | 15.4°C | 13.9°C | 12.4°C | 21.7°C | 11.5°C | 69 mm | 78% | 5.5 m/s | 6 |
| 2000 | 18.6°C | 16.5°C | 14.3°C | 29.4°C | 12.4°C | 27 mm | 72% | 5.2 m/s | 7.9 |
| 1999 | 17.9°C | 16.0°C | 14.1°C | 27.7°C | 12.2°C | 49 mm | 75% | 6 m/s | 6.8 |
| 1998 | 18.3°C | 16.1°C | 13.9°C | 29.1°C | 12.1°C | 37 mm | 76% | 5.5 m/s | 6.8 |
| 1997 | 16.9°C | 15.2°C | 13.6°C | 21.4°C | 12.8°C | 19 mm | 78% | 5.5 m/s | 6.9 |
| 1996 | 16.5°C | 14.4°C | 12.2°C | 24.9°C | 10.6°C | 29 mm | 72% | 5 m/s | 7.3 |
| 1995 ❄️ | 15.5°C | 13.9°C | 12.3°C | 22.5°C | 11.2°C | 58 mm | 76% | 5.8 m/s | 6.4 |
| 1994 | 19.2°C | 16.6°C | 14.1°C | 30.4°C | 10.4°C | 47 mm | 71% | 4.7 m/s | 7.3 |
| 1993 | 17.2°C | 15.1°C | 13.0°C | 26.5°C | 11.3°C | 81 mm | 76% | 5.4 m/s | 6.7 |
| 1992 | 17.9°C | 16.0°C | 14.0°C | 22.9°C | 11.4°C | 67 mm | 83% | 5.6 m/s | 5.9 |
| 1991 | 16.7°C | 14.8°C | 13.0°C | 26.5°C | 11.1°C | 38 mm | 79% | 5 m/s | 6.5 |
| 1990 | 18.1°C | 15.9°C | 13.7°C | 24.7°C | 11.1°C | 38 mm | 77% | 5.8 m/s | 6.9 |
| 1989 | 18.4°C | 16.2°C | 14.0°C | 24.7°C | 12.3°C | 29 mm | 74% | 5.5 m/s | 7.6 |
| 1988 | 18.4°C | 16.2°C | 14.0°C | 26.9°C | 12.0°C | 36 mm | 75% | 4.8 m/s | 6.9 |
| 1987 | 17.4°C | 15.2°C | 13.0°C | 26.5°C | 9.9°C | 69 mm | 74% | 5.3 m/s | 6.6 |
| 1986 | 16.9°C | 14.7°C | 12.5°C | 26.6°C | 10.8°C | 111 mm | 76% | 5.7 m/s | 6.5 |
| 1985 | 17.8°C | 15.9°C | 13.9°C | 23.8°C | 12.5°C | 124 mm | 79% | 5.7 m/s | 6.6 |
| 1984 | 17.3°C | 15.2°C | 13.1°C | 23.0°C | 10.9°C | 48 mm | 76% | 6.5 m/s | 6.9 |
| 1983 | 18.5°C | 16.3°C | 14.0°C | 27.8°C | 11.5°C | 20 mm | 74% | 4.5 m/s | — |
| 1982 | 17.7°C | 15.4°C | 13.1°C | 26.7°C | 11.0°C | 19 mm | 74% | 5.3 m/s | — |
| 1981 | 18.4°C | 16.2°C | 13.9°C | 27.7°C | 12.1°C | 18 mm | 73% | 5.2 m/s | — |
Actual recorded December data for each year, 1981–2025 — sourced from NASA POWER.
The average high in December is around 17.9°C with lows near 13.7°C (mean 15.8°C), based on 45 years of NASA POWER data.
December averages 49 mm of rainfall in Portland, one of the drier months. The wettest on record was 125 mm in 2010.
The hottest December reached 32.9°C in 2006. The coldest dipped to 9.9°C in 1987.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average December temperatures have risen by about 0.2°C. Daytime highs moved from 17.9°C to 18°C and overnight lows from 13.6°C to 13.9°C over the same span.
December is one of the warmer months of the year in Portland and one of the drier months, so plan for around 17.9°C daytime highs and 13.7°C at night.
Not quite — December is the 9th coolest month in Portland, averaging 15.8°C.
For December in Portland, pack light layers you can adjust through the day, with typical highs of 17.9°C and lows of 13.7°C.
Relative humidity in December averages 75% — quite humid.
Average wind speed in December is 5.4 m/s. The windiest December on record averaged 6.5 m/s (1984).
The wettest December on record was 2010 with 125 mm. On average, December sees 49 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.
