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December Weather in Sullivan, United States

Last updated: June 24, 2025

In December, the average temperature in Sullivan, United States hovers around 3°C (37°F). While you may experience chilling lows of -19°C (-2°F), the mercury can also rise to a pleasant 19°C (66°F). Expect about 64 mm (2.5 in) of precipitation over approximately 9 days, contributing to an average humidity level of 87%. Stay prepared for a mix of chilly and mild weather!

December Temperature in Sullivan

In December in Sullivan, the average temperature is 3°C (37°F). The maximum can reach 19°C (66°F), while the minimum can drop as low as -19°C (-2°F). Be prepared for a wide range of temperatures if you're planning to travel during this time.

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

The chart illustrates December temperature patterns in Sullivan, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Sullivan, December typically has an average temperature of 3°C (37°F), with highs reaching up to 19°C (66°F) and lows dropping to around -19°C (-2°F).
JanFebMarAprMayJunJulAugSepOctNovDec303344536675787471584237
Data source: Temperature data for Sullivan 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 Sullivan

In Sullivan in December, the precipitation amount is 64 mm (2.5 in) over a span of 9 days.

December Precipitation Trends in Sullivan

The chart displays monthly precipitation patterns in Sullivan, 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 Sullivan, December typically receives around 64 mm (2.5 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec7979127125138108116128691238964
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Sullivan

In Sullivan in December, humidity is 87%. With an average temperature of 3°C (37°F), this humidity feels like a damp chill that clings to your skin, making outdoor activities uncomfortable and necessitating proper layers to stay warm while navigating the wet conditions.

December Average Humidity in Sullivan

This chart illustrates the average monthly humidity levels in Sullivan, 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 Sullivan is approximately 87%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%82%84%83%80%83%82%83%79%79%88%87%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Sullivan

In Sullivan 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 Sullivan, you can check the information here.

Maximum UV Index Levels in Sullivan for December

The chart shows the monthly maximum UV Index (UVI) for Sullivan 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 Sullivan typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910111098643
Data source: Sullivan 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 Sullivan Compares to Other Months

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

This table compares monthly weather conditions in Sullivan, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (30°F)79 mm (3.1 inches)84%moderate
February Weather0°C (33°F)79 mm (3.1 inches)82%moderate
March Weather7°C (44°F)127 mm (5.0 inches)84%high
April Weather12°C (53°F)125 mm (4.9 inches)83%very high
May Weather19°C (66°F)138 mm (5.4 inches)80%very high
June Weather24°C (76°F)108 mm (4.2 inches)83%extreme
July Weather25°C (78°F)116 mm (4.6 inches)82%very high
August Weather24°C (75°F)128 mm (5.0 inches)82%very high
September Weather22°C (71°F)69 mm (2.7 inches)79%very high
October Weather14°C (58°F)123 mm (4.8 inches)79%high
November Weather6°C (42°F)89 mm (3.5 inches)88%moderate
December Weather3°C (37°F)64 mm (2.5 inches)87%moderate

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