December Weather in Helena, United States

Last updated: June 24, 2025

In December, the average temperature in Helena, United States hovers around 9°C (49°F). Expect a minimum chill of -8°C (19°F) and a warm maximum of 26°C (80°F). Rainfall can add to the atmosphere, with 144 mm (5.7 in) expected over 10 days. Additionally, the humidity remains notably high at 88%, creating a unique, if not slightly damp, experience.

December Temperature in Helena

In December in Helena, the average temperature is 9°C (49°F). Maximums can reach 26°C (80°F), and minimums can be as low as -8°C (19°F). This diverse temperature range makes Helena an interesting destination for travelers who appreciate both mild and chilly weather experiences.

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 9°C (49°F), with highs reaching up to 26°C (80°F) and lows dropping to around -8°C (19°F).

Data source: Temperature data for Helena generated using information from the Copernicus Climate Change Service.

December Precipitation in Helena

In Helena in December, the precipitation amount is 144 mm (5.7 in) over a duration of 10 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 144 mm (5.7 inches) of precipitation spread over approximately 10 days.

Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

December Humidity in Helena

In Helena in December, humidity is 88%. With an average temperature of 9°C (49°F), this humidity feels like a damp chill that seeps into your bones, making traveling uncomfortable and requiring extra layers to stay warm and dry.

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.

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.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	7°C (44°F)	107 mm (4.2 inches)	84%	moderate
February Weather	9°C (48°F)	185 mm (7.3 inches)	83%	high
March Weather	14°C (57°F)	172 mm (6.8 inches)	81%	very high
April Weather	17°C (62°F)	146 mm (5.7 inches)	81%	very high
May Weather	23°C (73°F)	138 mm (5.5 inches)	83%	extreme
June Weather	26°C (79°F)	133 mm (5.2 inches)	83%	extreme
July Weather	28°C (82°F)	124 mm (4.9 inches)	81%	extreme
August Weather	27°C (81°F)	114 mm (4.5 inches)	74%	very high
September Weather	25°C (77°F)	92 mm (3.6 inches)	71%	very high
October Weather	19°C (66°F)	111 mm (4.4 inches)	76%	high
November Weather	11°C (52°F)	82 mm (3.2 inches)	84%	high
December Weather	9°C (49°F)	144 mm (5.7 inches)	88%	moderate