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December Weather in St. Marys, United States

Last updated: June 24, 2025

In St. Marys, United States, the average temperature in December hovers around 15°C (59°F), with a minimum dipping to 0°C (32°F) and a maximum reaching 26°C (78°F). Expect 86 mm (3.4 in) of precipitation spread over 7 days, contributing to an average humidity level of 85%. Prepare for a mix of cozy and refreshing weather during your stay!

December Temperature in St. Marys

In December in St. Marys, the average temperature is 15°C (59°F). The maximum can reach 26°C (78°F) and the minimum can be as low as 0°C (32°F). This makes it an ideal time for travelers to enjoy pleasant weather while exploring the beautiful sights of St. Marys.

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

The chart illustrates December temperature patterns in St. Marys, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In St. Marys, December typically has an average temperature of 15°C (59°F), with highs reaching up to 26°C (78°F) and lows dropping to around 0°C (32°F).
JanFebMarAprMayJunJulAugSepOctNovDec566064697579818180756459
Data source: Temperature data for St. 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 St. Marys

In St. Marys in December, the total precipitation amount is 86 mm (3.4 in) over a span of 7 days.

December Precipitation Trends in St. Marys

The chart displays monthly precipitation patterns in St. 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 St. Marys, December typically receives around 86 mm (3.4 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec5171446680145170172155788086
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in St. Marys

In St. Marys in December, humidity is 85%. With an average temperature of 15°C (59°F), this humidity feels like a warm, damp blanket wrapping around you, making traveling quite uncomfortable and sticky. Be prepared to take frequent breaks and stay hydrated as you navigate the lush, but humid environment.

December Average Humidity in St. Marys

This chart illustrates the average monthly humidity levels in St. 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 St. Marys is approximately 85%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%79%78%73%72%74%82%82%83%79%82%85%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in St. Marys

In St. Marys in December, the maximum UV index reaches 4, which corresponds to a moderate Exposure Category. With a time to burn of 30 minutes, it’s important to take precautions to protect your skin. You can find more details in the Hourly UV Index in St. Marys for better planning.

Maximum UV Index Levels in St. Marys for December

The chart shows the monthly maximum UV Index (UVI) for St. 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 St. Marys typically reaches 4, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec579101111111110864
Data source: St. 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 St. Marys Compares to Other Months

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

This table compares monthly weather conditions in St. Marys, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather13°C (56°F)51 mm (2.0 inches)84%moderate
February Weather16°C (61°F)71 mm (2.8 inches)79%high
March Weather18°C (64°F)44 mm (1.7 inches)78%very high
April Weather21°C (69°F)66 mm (2.6 inches)72%very high
May Weather24°C (75°F)80 mm (3.2 inches)72%extreme
June Weather26°C (80°F)145 mm (5.7 inches)74%extreme
July Weather27°C (81°F)170 mm (6.7 inches)82%extreme
August Weather27°C (82°F)172 mm (6.8 inches)82%extreme
September Weather26°C (80°F)155 mm (6.1 inches)83%very high
October Weather24°C (75°F)78 mm (3.1 inches)79%very high
November Weather18°C (64°F)80 mm (3.1 inches)82%high
December Weather15°C (59°F)86 mm (3.4 inches)85%moderate

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