Last updated: June 24, 2025
In December, the average temperature in Portland, United States hovers around 2°C (35°F). Expect a chilly chill with minimums dropping to -22°C (-7°F) and occasional highs reaching 17°C (63°F). With 67 mm (2.7 in) of precipitation spread over 9 days, you might want to keep that umbrella handy! Additionally, the air tends to feel quite damp, with an average humidity of 86%.
In December in Portland, the average temperature is 2°C (35°F), with maximums reaching up to 17°C (63°F) and minimums dropping as low as -22°C (-7°F). Travelers should be prepared for a wide range of temperatures and pack accordingly for both warmer and colder conditions.
In Portland in December, the precipitation amount is 67 mm (2.7 in), occurring over a span of 9 days.
In Portland in December humidity is 86%. With an average temperature of 2°C (35°F), this humidity feels like a damp chill that seeps into your bones, making traveling quite uncomfortable as your clothes cling to you and the cold air cuts through any warmth you try to find.
In Portland in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Portland, you can visit Hourly UV Index in Portland.
UV Risk Categories
Weather in Portland varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Portland, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -2°C (29°F) | 74 mm (2.9 inches) | 85% | moderate |
| February Weather | 0°C (32°F) | 88 mm (3.4 inches) | 85% | moderate |
| March Weather | 5°C (42°F) | 101 mm (4.0 inches) | 86% | high |
| April Weather | 10°C (51°F) | 93 mm (3.7 inches) | 87% | very high |
| May Weather | 17°C (63°F) | 127 mm (5.0 inches) | 81% | very high |
| June Weather | 22°C (73°F) | 114 mm (4.5 inches) | 82% | extreme |
| July Weather | 24°C (76°F) | 101 mm (4.0 inches) | 81% | very high |
| August Weather | 23°C (74°F) | 102 mm (4.0 inches) | 79% | very high |
| September Weather | 20°C (69°F) | 75 mm (2.9 inches) | 78% | very high |
| October Weather | 14°C (57°F) | 97 mm (3.8 inches) | 81% | high |
| November Weather | 5°C (42°F) | 82 mm (3.2 inches) | 89% | moderate |
| December Weather | 2°C (35°F) | 67 mm (2.7 inches) | 86% | low |