December Weather in Portland, United States

Last updated: February 24, 2025

December in Portland, United States, presents a mix of cool temperatures and ample precipitation, creating a distinctly chilly atmosphere. The maximum temperature reaches around 16°C (60°F), while the average hovers at a brisk 5°C (41°F). Nights can plunge to a minimum of -5°C (24°F), adding a crisp bite to the air. Throughout the month, the city sees an impressive 183 mm (7.2 in) of rainfall, spread over 19 days, contributing to an overall humidity level of 87%. This blend of cold and wet makes December a quintessential winter month, perfect for cozy indoor activities and festive celebrations.

December Temperature in Portland

In December, Portland experiences a chill as temperatures begin to dip with minimums reaching as low as -5°C (24°F). The average temperature settles at 5°C (41°F), while maximums peak at 16°C (60°F), providing a crisp atmosphere that hints at the arrival of winter. This month often marks a transitional period from the milder conditions of late autumn, with colder nights becoming more common. As the year draws to a close, residents should be prepared for a cozy December, where layering up becomes essential for enjoying the festive spirit amid the cool air. Overall, while chilly, December’s temperatures offer a refreshing contrast and an invitation to embrace the winter season in Portland.

December Weather in Portland: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Portland, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec424146515864697064534641
Data source: Temperature data for Portland generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Portland

December in Portland marks the peak of the rainy season, with precipitation reaching 183 mm (7.2 in) spread over 19 days—the highest monthly totals of the year. This trend reflects a notable increase compared to the preceding months, such as November, which received 155 mm over 18 days. As the year closes, the city experiences a marked transition from the relatively drier summer and early autumn months, where rainfall dips significantly to just 6 mm in July. With winter fully upon the Pacific Northwest, residents can expect a landscape transformed by consistent rain, reinforcing Portland's reputation for lush greenery and vibrant ecosystems.

December Precipitation Trends in Portland

The chart displays monthly precipitation patterns in Portland, with values for each month alongside December's data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December's conditions compare to those of other months.
JanFebMarAprMayJunJulAugSepOctNovDec16317213511758466862105155184
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Portland

In December, Portland experiences a notable increase in humidity, reaching 87%, mirroring the trend set in November. This month marks the return of the city's characteristic dampness after the drier spell of late summer and early fall, where humidity dipped as low as 71% in September. As the year draws to a close, the consistent high humidity of December and November reflects Portland's transition into its wetter winter months, reinforcing its reputation for a cool, moist climate. The relatively stable humidity levels throughout the year, mostly lingering in the low to mid-80s, showcase the city’s distinctive maritime influence, making it a unique backdrop for winter festivities.

December Average Humidity in Portland

This chart illustrates the average monthly humidity levels in Portland, with December's data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, allowing you to see how December's humidity levels compare to other months.
JanFebMarAprMayJunJulAugSepOctNovDec85%84%85%83%83%84%82%74%71%81%87%87%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Portland

In December, the UV Index in Portland drops to a low level of 2, indicating a significant decrease in sun exposure compared to the vibrant summer months. With a burn time of 45 minutes, residents can enjoy outdoor activities with less concern for skin damage. This trend of reduced UV levels continues from November's moderate index of 3, reflecting a seasonal pattern where protective measures become less critical as winter sets in. As the year progresses, the UV Index notably peaks in the summer, reaching very high levels of 9 and 10 from May through August, before gradually tapering off in the fall and winter. For more detailed information, check out the comprehensive details at Portland UV Index.

Maximum UV Index Levels in Portland for December

The chart shows the monthly maximum UV Index (UVI) for Portland in December, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues.
JanFebMarAprMayJunJulAugSepOctNovDec23569101087532
Data source: Portland December UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

December Sunshine in Portland

December in Portland experiences a notable dip in sunshine, with only 115 hours illuminating the month. As the year wraps up, this decline follows a gradual upward trend from the previous seasons, peaking in the vibrant summer months of June and July, where residents basked in a generous 318 and 374 hours respectively. This latter half of the year sees the sun's embrace waning, particularly stark between October's 211 hours and November’s 136 hours. While December's shorter days herald the onset of winter, they also invite a cozy charm, making the fleeting moments of sunlight all the more cherished as the city prepares for the new year ahead.

Monthly Sunshine Duration in Portland: December Highlighted

The December sunshine duration represents the total number of hours Portland experiences direct sunlight during the month of December, excluding cloudy or obstructed periods. This chart compares the sunshine duration of December with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec88h123h195h229h282h318h374h335h268h211h136h115h
Data source: Portland December Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Portland During December

When it comes to December weather in Portland, the likelihood of catching some sunshine is notably low, standing at just 14%. As we transition from the vibrant hues of autumn into winter, the trend continues from November's already gloomy 16% chance of sun, further emphasizing the region's characteristic overcast skies during this time of year. Comparatively, December's chances pale in contrast to the sunnier months that follow—such as July, which boasts a robust 74% likelihood of clear skies. As Portlanders prepare for the holiday season, it's clear that sun-seeking will require a bit of patience, as December's weather typically veils the city in a cozy, cloud-laden embrace.

Percentage of Sunny Days in December in Portland

The chart illustrates the percentage of sunny days in Portland throughout the year, with December highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Portland experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec16%17%38%54%37%63%75%58%50%30%16%14%
Data source: Portland December chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Portland in December

In Portland, the daylight duration undergoes a noticeable transformation throughout the year, with December marking a low point at just 8 hours of daylight. This reduction in light stands in stark contrast to the longest days of summer, where June and July reclaim an impressive 15 hours each. As the year progresses from January's 9 hours to December's decline, the trend highlights a gentle yet persistent ebb and flow of sunlight. The gradual increase in daylight from the winter solstice, alongside the eventual return to longer days in spring, reflects the rhythmic cycle of the seasons, inviting a sense of renewal and hope as the days begin to lengthen again.

Average Daylight Hours in Portland for December

The chart illustrates the variation in daylight duration in Portland throughout the year, with December highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec9h 9m10h 24m11h 57m13h 33m14h 55m15h 35m15h 13m13h 59m12h 27m10h 52m9h 28m8h 45m
Data source: Portland daylight hours, calculated by summing the hours between sunrise and sunset for each day.

December Winds in Portland

As December arrives in Portland, the wind begins to pick up slightly, with average speeds reaching 2.7 m/s (or about 6 mph). This marks a noticeable trend as the year closes, showing a steady increase in wind speed compared to the calmer months of spring and early summer. Throughout the year, wind speeds fluctuate modestly, generally hovering around 5 mph during the warmer months. However, from October onwards, a shift occurs, with November and December both recording sustained winds of 6 mph. This slight uptick in December's breezy conditions creates a refreshing atmosphere, enhancing the city's vibrant winter landscape and inviting residents and visitors alike to embrace the season's chill.

Average December Wind Speed in Portland

The chart displays monthly wind speed patterns in Portland, with values for each month shown alongside December's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how December's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec2.42.92.22.22.42.22.42.22.32.72.82.7 m/s
Data source: Portland December wind data, generated using information from the Copernicus Climate Change Service.

How December Weather in Portland Compares to Other Months

The weather in Portland changes throughout the year, offering a unique experience in each season. Below is a month-by-month comparison of December's weather with other months, highlighting differences in temperature, precipitation, and other key factors. Click on each section to discover seasonal trends in Portland and find detailed weather information for every month.

In December, the weather is relatively mild with an average temperature of 5°C (41°F) and a maximum of 16°C (60°F), but it also experiences a low of -5°C (24°F). Precipitation is significant, totaling 183 mm (7.2 in) over 19 days, and humidity remains high at 87%.

Contrastingly, January brings colder conditions, with a minimum temperature dropping to -14°C (7°F), although the average remains stable at 5°C (42°F) and the maximum slightly decreases to 15°C (59°F). Rainfall is slightly less at 163 mm (6.4 in) over 17 days, and humidity is a touch lower at 85%. For more detailed insights into Portland weather in January, you can explore further.

In December, temperatures in the region range from a minimum of -5°C (24°F) to a maximum of 16°C (60°F), with an average temperature of 5°C (41°F). The month experiences significant precipitation, totaling 183 mm (7.2 in) over 19 days, combined with high humidity levels averaging 87%.

In contrast, February sees slightly colder temperatures, with minimums dipping to -7°C (19°F) and maximums reaching 17°C (63°F), while maintaining the same average of 5°C (41°F). Precipitation decreases slightly to 172 mm (6.8 in), still spanning 19 days, and humidity levels are also lower at 84%.

For a more detailed look at the weather trends, you can explore Portland weather in February.

In December, the weather tends to be quite cold, with temperatures ranging from a minimum of -5°C (24°F) to a maximum of 16°C (60°F), averaging around 5°C (41°F). The month sees considerable precipitation, totaling 183 mm (7.2 in) over 19 days, and an average humidity of 87%.

In contrast, March brings slightly milder conditions, with temperatures ranging from a minimum of -4°C (26°F) to a maximum of 24°C (75°F), averaging 8°C (46°F). Precipitation decreases to 135 mm (5.3 in) over 17 days, and the humidity remains fairly high at 85%. For those interested in experiencing the transition from winter to spring, here is more about Portland weather in March.

December weather is characterized by cooler temperatures, ranging from a minimum of -5°C (24°F) to a maximum of 16°C (60°F), with an average of 5°C (41°F). December also sees significant precipitation, totaling 183 mm (7.2 in) over 19 days, accompanied by high humidity levels at 87%. In contrast, April experiences a milder climate, with temperatures ranging from a minimum of -1°C (31°F) to a maximum of 29°C (84°F) and an average of 11°C (51°F). Precipitation is lower in April, at 117 mm (4.6 in) over 15 days, and humidity decreases slightly to 83%. For a detailed overview of weather trends, check out Portland weather in April.

December and May present strikingly different weather patterns. In December, temperatures range from a chilly -5°C (24°F) to a milder 16°C (60°F), with an average of 5°C (41°F), accompanied by significant precipitation of 183 mm (7.2 in) over 19 days and a high humidity of 87%. In contrast, May experiences warmer temperatures, with a minimum of 2°C (36°F), an average of 14°C (58°F), and a peak of 32°C (90°F). The month sees much less precipitation, totaling 58 mm (2.3 in) across 10 days, and slightly lower humidity at 83%. For a closer look at the specific conditions in May, check out Portland weather in May.

When comparing the weather in December and June, there is a stark contrast in temperatures and precipitation levels. December tends to be much colder, with average temperatures ranging from a chilly -5°C (24°F) to a mild 16°C (60°F), accompanied by significant precipitation of 183 mm (7.2 in) over 19 rainy days and high humidity at 87%. In contrast, June offers a much warmer climate, with temperatures typically ranging from a minimum of 6°C (43°F) to a balmy maximum of 47°C (118°F). The month also sees considerably less precipitation, averaging just 46 mm (1.8 in) over 8 days and slightly lower humidity at 83%. These differences highlight the diverse experiences of weather in Portland throughout the year, as detailed further at Portland weather in June.

December and July showcase contrasting weather patterns. December features a chilly climate with temperatures ranging from a minimum of -5°C (24°F) to a maximum of 16°C (60°F), accompanied by significant precipitation of 183 mm (7.2 in) over 19 days. In contrast, July brings much warmer conditions, with temperatures fluctuating between a minimum of 9°C (49°F) and a sweltering maximum of 37°C (99°F). Rain is scarce during this month, with only 6 mm (0.2 in) falling over just one day. Both months experience high humidity levels, at 87% in December and 82% in July, but the overall feel is markedly different. For more details on July's conditions, visit Portland weather in July.

December and August present strikingly contrasting weather patterns. In December, temperatures range from a chilly -5°C (24°F) to a mild 16°C (60°F), with an average of about 5°C (41°F). The month is also characterized by significant precipitation, totaling 183 mm (7.2 in) over 19 days, accompanied by high humidity levels at 87%. In sharp contrast, August boasts warmer temperatures, with a minimum of 9°C (48°F) and a maximum that can soar up to 40°C (104°F), averaging around 21°C (70°F). Rainfall is minimal during this month, with only 8 mm (0.3 in) recorded over just 2 days, and humidity levels are notably lower at 74%. For more detailed information, check out Portland weather in August.

September and December present starkly contrasting weather conditions. In September, temperatures range from a minimum of 6°C (42°F) to a maximum of 35°C (95°F), with an average of 18°C (64°F). This month sees relatively low precipitation at 62 mm (2.4 in) over just 8 days and a humidity level of 71%, creating a warm and pleasant atmosphere. In contrast, December features much cooler temperatures, with a minimum of -5°C (24°F) and a maximum of 16°C (60°F), averaging just 5°C (41°F). The month is marked by higher precipitation levels at 183 mm (7.2 in) spread over 19 days, along with increased humidity at 87%. These differences make September a time of warmth and relative dryness, while December brings cold, damp, and more variable weather. For more insights, check out Portland weather in September.

When comparing the weather in December and October, it's evident that December is significantly colder and wetter. While October boasts milder temperatures with a minimum of -2°C (29°F) and an average high of 26°C (79°F), December tends to see a minimum of -5°C (24°F) and an average high of only 16°C (60°F). Additionally, October experiences less precipitation, with 105 mm (4.1 in) over 12 days, compared to December's 183 mm (7.2 in) over 19 days. The humidity is also slightly lower in October at 81%, versus December's 87%. For more details on October's weather, you can visit Portland weather in October.

In comparing the weather of December and November, we can see that December tends to be slightly colder, with average temperatures dropping from 8°C (47°F) in November to 5°C (41°F) in December. While both months share the same minimum temperature of -5°C (24°F), November experiences higher maximum temperatures, reaching up to 19°C (67°F) compared to December's 16°C (60°F). Additionally, precipitation increases in December, totaling 183 mm (7.2 in) over 19 days, in contrast to November's 155 mm (6.1 in) over 18 days. Interestingly, humidity remains consistent for both months at 87%. For more details on November's specific weather patterns, you can visit Portland weather in November.

Compare Portland's Climate with Cities Worldwide

Conclusion: What to Expect From December Weather in Portland

In December, Portland transforms into a winter wonderland, where temperatures dip significantly compared to the milder months of fall. With an average chill of about 5°C, residents linger beneath the weight of heavy overcast clouds, accompanied by high humidity levels reaching 87%. This month is marked by frequent rainfall, as 183 mm of precipitation falls over 19 days, making it one of the wettest times of the year. As the city embraces the festive season, the cool air and consistent showers set a cozy yet invigorating atmosphere. For a deeper understanding of what to expect throughout the year, visit Portland Climate.