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December Weather in Saint Marys, United States

Last updated: June 24, 2025

In December, the average temperature in Saint Marys, United States hovers around 3°C (37°F). While you may experience chilly minimums of -18°C (0°F), the warmth can occasionally peak at 23°C (73°F). Expect about 30 mm (1.2 in) of precipitation over 3 days, and prepare for a rather humid atmosphere with an average humidity of 84%.

December Temperature in Saint Marys

In December in Saint Marys, the average temperature is 3°C (37°F), with maximums reaching up to 23°C (73°F) and minimums dropping as low as -18°C (0°F). Travelers should be prepared for a wide range of temperatures, ensuring they pack both warm and lightweight clothing for their visit.

December Weather in Saint Marys: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Saint Marys, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Saint Marys, December typically has an average temperature of 3°C (37°F), with highs reaching up to 23°C (73°F) and lows dropping to around -18°C (0°F).
JanFebMarAprMayJunJulAugSepOctNovDec313246546577817772564437
Data source: Temperature data for Saint Marys 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 Saint Marys

In Saint Marys in December, the precipitation amount is 30 mm (1.2 in) over the course of 3 days.

December Precipitation Trends in Saint Marys

The chart displays monthly precipitation patterns in Saint Marys, 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 Saint Marys, December typically receives around 30 mm (1.2 inches) of precipitation spread over approximately 3 days.
JanFebMarAprMayJunJulAugSepOctNovDec382793782059690130801093330
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Saint Marys

In Saint Marys in December humidity is 84%. With an average temperature of 3°C (37°F), this humidity feels like a damp chill that seeps into your bones, making outdoor excursions brisk and invigorating, yet requiring extra layers to stay comfortable.

December Average Humidity in Saint Marys

This chart illustrates the average monthly humidity levels in Saint Marys, 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 Saint Marys is approximately 84%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec76%78%70%73%82%82%81%78%71%71%81%84%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Saint Marys

In Saint Marys 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 Saint Marys, you can check the information here.

Maximum UV Index Levels in Saint Marys for December

The chart shows the monthly maximum UV Index (UVI) for Saint Marys 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 Saint Marys typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3569101111109643
Data source: Saint Marys 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 Saint Marys Compares to Other Months

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

This table compares monthly weather conditions in Saint Marys, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (31°F)38 mm (1.5 inches)76%moderate
February Weather0°C (32°F)27 mm (1.1 inches)77%moderate
March Weather8°C (46°F)93 mm (3.7 inches)70%high
April Weather12°C (54°F)78 mm (3.1 inches)73%very high
May Weather19°C (66°F)205 mm (8.1 inches)82%very high
June Weather25°C (78°F)96 mm (3.8 inches)82%extreme
July Weather27°C (81°F)90 mm (3.6 inches)81%extreme
August Weather25°C (77°F)130 mm (5.1 inches)78%very high
September Weather22°C (72°F)80 mm (3.1 inches)71%very high
October Weather13°C (57°F)109 mm (4.3 inches)71%high
November Weather6°C (44°F)32 mm (1.3 inches)81%moderate
December Weather3°C (37°F)30 mm (1.2 inches)84%moderate

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