Last updated: June 24, 2025
In December, the average temperature in Portland, United States hovers around 0°C (32°F), making it a chilly experience. Daily temperatures can swing from a bone-chilling -25°C (-14°F) to a relatively mild 16°C (62°F). This month also brings about 63 mm (2.5 in) of precipitation spread over 10 days, with an average humidity of 86%, resulting in a damp and crisp atmosphere. Embrace the season, but don’t forget your warm layers!
In December in Portland, the average temperature is 0°C (32°F). The maximum can reach 16°C (62°F), and the minimum can be as low as -25°C (-14°F). Be prepared for a wide range of temperatures when traveling to Portland during this month.
In Portland in December, the precipitation amount is 63 mm (2.5 in) over a span of 10 days.
In Portland in December humidity is 86%. With an average temperature of 0°C (32°F), this humidity feels like a biting chill that seeps into your bones, making travel feel uncomfortable and damp, as the cold air combines with the moisture to create a brisk sensation that may deter outdoor exploration.
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 | -3°C (26°F) | 67 mm (2.6 inches) | 87% | low |
| February Weather | -3°C (27°F) | 71 mm (2.8 inches) | 87% | moderate |
| March Weather | 3°C (37°F) | 68 mm (2.7 inches) | 86% | moderate |
| April Weather | 8°C (47°F) | 87 mm (3.4 inches) | 87% | very high |
| May Weather | 15°C (60°F) | 136 mm (5.4 inches) | 82% | very high |
| June Weather | 21°C (70°F) | 106 mm (4.2 inches) | 81% | very high |
| July Weather | 24°C (75°F) | 82 mm (3.2 inches) | 78% | very high |
| August Weather | 22°C (72°F) | 68 mm (2.7 inches) | 79% | very high |
| September Weather | 18°C (65°F) | 108 mm (4.3 inches) | 79% | high |
| October Weather | 12°C (53°F) | 127 mm (5.0 inches) | 82% | moderate |
| November Weather | 4°C (39°F) | 64 mm (2.5 inches) | 87% | moderate |
| December Weather | 0°C (32°F) | 63 mm (2.5 inches) | 86% | low |