Last updated: June 24, 2025
In Portland, United States during December, the average temperature hovers around -8°C (18°F). Expect a chilling minimum of -33°C (-27°F), while the maximum can reach a surprising 10°C (50°F). Precipitation averages 39 mm (1.5 in) spread over 8 days, with humidity levels at a brisk 86%. Prepare for a truly wintry experience!
In December in Portland, the average temperature is -8°C (18°F). Maximums can reach 10°C (50°F), while minimums can plummet to -33°C (-27°F). It’s essential to pack warm clothing if you plan to travel during this chilly time.
In Portland in December, the precipitation amount is 39 mm (1.5 in) over the course of 8 days.
In Portland in December, humidity is 86%. With an average temperature of -8°C (18°F), this humidity feels like a biting chill that seeps into your bones, making travel uncomfortable and frigid, as the damp air accentuates the cold, creating a sharp contrast that can be quite challenging for outdoor activities.
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 | -12°C (10°F) | 18 mm (0.7 inches) | 90% | low |
| February Weather | -13°C (9°F) | 19 mm (0.8 inches) | 92% | moderate |
| March Weather | -3°C (27°F) | 27 mm (1.1 inches) | 85% | moderate |
| April Weather | 4°C (39°F) | 41 mm (1.6 inches) | 81% | high |
| May Weather | 13°C (56°F) | 55 mm (2.2 inches) | 75% | very high |
| June Weather | 20°C (69°F) | 91 mm (3.6 inches) | 79% | very high |
| July Weather | 22°C (72°F) | 62 mm (2.4 inches) | 76% | very high |
| August Weather | 20°C (68°F) | 81 mm (3.2 inches) | 78% | very high |
| September Weather | 15°C (60°F) | 68 mm (2.7 inches) | 77% | high |
| October Weather | 6°C (44°F) | 79 mm (3.1 inches) | 79% | moderate |
| November Weather | -2°C (28°F) | 21 mm (0.8 inches) | 86% | moderate |
| December Weather | -8°C (18°F) | 39 mm (1.5 inches) | 86% | low |