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December Weather in Portland, United States

Last updated: June 24, 2025

In December, the average temperature in Portland, United States hovers around 2°C (35°F), with minimums dipping to -16°C (4°F) and maximums reaching as high as 17°C (62°F). Expect 106 mm (4.2 in) of precipitation spread over 11 days, accompanied by an average humidity level of 85%.

December Temperature in Portland

In December in Portland, the average temperature is 2°C (35°F). Maximums can reach 17°C (62°F), while minimums can drop as low as -16°C (4°F). Travelers should be prepared for a wide range of temperatures and dress in layers to stay comfortable.

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. In Portland, December typically has an average temperature of 2°C (35°F), with highs reaching up to 17°C (62°F) and lows dropping to around -16°C (4°F).
JanFebMarAprMayJunJulAugSepOctNovDec313439506069757367574235
Data source: Temperature data for Portland generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Portland

In Portland in December, the precipitation amount is 106 mm (4.2 in) spread over a duration of 11 days.

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. In Portland, December typically receives around 106 mm (4.2 inches) of precipitation spread over approximately 11 days.
JanFebMarAprMayJunJulAugSepOctNovDec71102941101369212412510714190106
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Portland

In Portland in December humidity is 85%. With an average temperature of 2°C (35°F), this humidity feels like a damp chill that permeates your clothing, making travel uncomfortable and requiring extra layers to stay warm and dry.

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, helping you understand how conditions vary by season. In December, average humidity in Portland is approximately 85%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec87%85%85%83%75%74%65%62%66%79%87%85%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Portland

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.

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. In December, the maximum UV index in Portland typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910101098642
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.

How December Weather in Portland Compares to Other Months

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.

This table compares monthly weather conditions in Portland, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (31°F)71 mm (2.8 inches)87%moderate
February Weather1°C (34°F)102 mm (4.0 inches)85%moderate
March Weather4°C (39°F)94 mm (3.7 inches)85%high
April Weather10°C (50°F)110 mm (4.3 inches)83%very high
May Weather16°C (61°F)135 mm (5.3 inches)75%very high
June Weather21°C (69°F)92 mm (3.6 inches)73%very high
July Weather24°C (75°F)124 mm (4.9 inches)65%very high
August Weather23°C (73°F)125 mm (4.9 inches)62%very high
September Weather19°C (67°F)107 mm (4.2 inches)66%very high
October Weather14°C (57°F)141 mm (5.5 inches)79%high
November Weather6°C (42°F)90 mm (3.5 inches)87%moderate
December Weather2°C (35°F)106 mm (4.2 inches)85%low

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