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December Weather in Helena, United States

Last updated: June 24, 2025

In December, the average temperature in Helena, United States hovers around 10°C (50°F), making it a typically cool time of year. Expect lows of -6°C (21°F) and highs reaching up to 25°C (76°F). With 142 mm (5.6 in) of precipitation spread over 12 days, you'll want to stay prepared for some rain. Additionally, the average humidity sits at a high 88%, adding to the chill in the air.

December Temperature in Helena

In December in Helena, the average temperature is 10°C (50°F), with a maximum that can reach 25°C (76°F) and a minimum that can dip as low as -6°C (21°F). This variation in temperatures makes it essential to pack layers for your travels, ensuring you stay comfortable no matter the weather.

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

The chart illustrates December temperature patterns in Helena, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Helena, December typically has an average temperature of 10°C (50°F), with highs reaching up to 25°C (76°F) and lows dropping to around -6°C (21°F).
JanFebMarAprMayJunJulAugSepOctNovDec475358637277808077685350
Data source: Temperature data for Helena 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 Helena

In Helena in December, the total precipitation amount is 142 mm (5.6 in), occurring over the course of 12 days.

December Precipitation Trends in Helena

The chart displays monthly precipitation patterns in Helena, 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 Helena, December typically receives around 142 mm (5.6 inches) of precipitation spread over approximately 12 days.
JanFebMarAprMayJunJulAugSepOctNovDec1121551341401081471231228513283142
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Helena

In Helena in December, humidity is 88%. With an average temperature of 10°C (50°F), this humidity feels like a damp chill that seeps into your bones, making outdoor exploration uncomfortable and encouraging travelers to seek cozy indoor activities instead.

December Average Humidity in Helena

This chart illustrates the average monthly humidity levels in Helena, 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 Helena is approximately 88%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%84%82%82%81%77%77%72%73%73%85%88%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Helena

In Helena 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 Helena for better planning.

Maximum UV Index Levels in Helena for December

The chart shows the monthly maximum UV Index (UVI) for Helena 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 Helena typically reaches 4, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec47810111111119864
Data source: Helena 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 Helena Compares to Other Months

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

This table compares monthly weather conditions in Helena, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather8°C (47°F)112 mm (4.4 inches)85%moderate
February Weather11°C (53°F)155 mm (6.1 inches)84%high
March Weather15°C (59°F)134 mm (5.3 inches)82%very high
April Weather17°C (64°F)140 mm (5.5 inches)82%very high
May Weather22°C (73°F)108 mm (4.2 inches)81%extreme
June Weather25°C (78°F)147 mm (5.8 inches)77%extreme
July Weather27°C (81°F)122 mm (4.8 inches)77%extreme
August Weather26°C (80°F)122 mm (4.8 inches)72%extreme
September Weather25°C (77°F)85 mm (3.3 inches)73%very high
October Weather20°C (68°F)132 mm (5.2 inches)73%very high
November Weather12°C (54°F)83 mm (3.3 inches)85%high
December Weather10°C (50°F)142 mm (5.6 inches)88%moderate

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