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December Weather in South Portland, United States

Last updated: June 24, 2025

In December, the average temperature in South Portland, United States hovers around 0°C (33°F). Expect chilly days with a minimum of -18°C (-1°F) and occasional highs reaching 13°C (57°F). During this time, precipitation totals about 144 mm (5.7 in) over 10 days, contributing to an average humidity of 81%. Prepare for a cool and damp climate!

December Temperature in South Portland

In December in South Portland, the average temperature is 0°C (33°F). The maximum can reach 13°C (57°F) and the minimum can be as low as -18°C (-1°F). Be sure to pack warm clothing if you're planning to visit during this time!

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

The chart illustrates December temperature patterns in South Portland, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In South Portland, December typically has an average temperature of 0°C (33°F), with highs reaching up to 13°C (57°F) and lows dropping to around -18°C (-1°F).
JanFebMarAprMayJunJulAugSepOctNovDec282934435262686963544232
Data source: Temperature data for South 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 South Portland

In South Portland in December, the precipitation amount is 144 mm (5.7 in) over a duration of 10 days.

December Precipitation Trends in South Portland

The chart displays monthly precipitation patterns in South 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 South Portland, December typically receives around 144 mm (5.7 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec971039114994801237577163130144
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in South Portland

In South Portland in December, humidity is 81%. With an average temperature of 0°C (33°F), this humidity feels like a damp chill enveloping you, making travel uncomfortable and the air heavy, leaving you craving warmth and dry conditions.

December Average Humidity in South Portland

This chart illustrates the average monthly humidity levels in South 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 South Portland is approximately 81%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%82%80%72%72%67%66%71%79%84%81%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in South Portland

In South 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 South Portland, you can visit Hourly UV Index in South Portland.

Maximum UV Index Levels in South Portland for December

The chart shows the monthly maximum UV Index (UVI) for South 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 South Portland typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2457910987532
Data source: South 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 South Portland Compares to Other Months

Weather in South Portland varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in South Portland, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in South Portland, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-2°C (28°F)97 mm (3.8 inches)86%low
February Weather-2°C (29°F)103 mm (4.1 inches)84%moderate
March Weather1°C (34°F)91 mm (3.6 inches)82%moderate
April Weather6°C (43°F)149 mm (5.9 inches)80%high
May Weather11°C (52°F)94 mm (3.7 inches)72%very high
June Weather17°C (62°F)80 mm (3.2 inches)72%very high
July Weather20°C (68°F)123 mm (4.9 inches)67%very high
August Weather20°C (69°F)75 mm (3.0 inches)66%very high
September Weather17°C (63°F)77 mm (3.0 inches)71%high
October Weather12°C (54°F)163 mm (6.4 inches)78%moderate
November Weather5°C (42°F)130 mm (5.1 inches)84%moderate
December Weather0°C (33°F)144 mm (5.7 inches)81%low

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