Last updated: June 24, 2025
In December, the average temperature in Portland, United States hovers around 7°C (45°F), with extremes ranging from a chilling -11°C (13°F) to a pleasant 23°C (73°F). Expect about 147 mm (5.8 in) of precipitation over 11 days, contributing to a relatively high average humidity of 88%. Prepare accordingly for a month that showcases the cool and varied climate of this intriguing location!
In December in Portland, the average temperature is 7°C (45°F). Maximums can reach 23°C (73°F) and minimums can be as low as -11°C (13°F). Be sure to pack layers to stay comfortable while exploring the diverse weather conditions.
In Portland in December, the total precipitation amount is 147 mm (5.8 in), occurring over the course of 11 days.
In Portland in December humidity is 88%. With an average temperature of 7°C (45°F), this humidity feels like a damp chill that seeps into your bones, making traveling uncomfortable as you navigate through a heavy, thick atmosphere that clings to your skin.
In Portland in December, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Portland, you can check the information here.
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 | 4°C (40°F) | 105 mm (4.1 inches) | 87% | moderate |
| February Weather | 7°C (44°F) | 185 mm (7.3 inches) | 86% | high |
| March Weather | 11°C (52°F) | 157 mm (6.2 inches) | 86% | high |
| April Weather | 15°C (59°F) | 150 mm (5.9 inches) | 82% | very high |
| May Weather | 21°C (70°F) | 122 mm (4.8 inches) | 82% | very high |
| June Weather | 25°C (77°F) | 141 mm (5.5 inches) | 83% | extreme |
| July Weather | 27°C (80°F) | 125 mm (4.9 inches) | 80% | extreme |
| August Weather | 25°C (78°F) | 124 mm (4.9 inches) | 74% | very high |
| September Weather | 23°C (74°F) | 125 mm (4.9 inches) | 71% | very high |
| October Weather | 17°C (63°F) | 138 mm (5.4 inches) | 78% | high |
| November Weather | 9°C (48°F) | 88 mm (3.4 inches) | 88% | moderate |
| December Weather | 7°C (45°F) | 147 mm (5.8 inches) | 88% | moderate |