December Weather in Umatilla, United States

Last updated: June 24, 2025

In December, the average temperature in Umatilla, United States hovers around 2°C (37°F). Expect a chilly range where minimums can plunge to -9°C (16°F), while maximums can reach a mild 20°C (68°F). Rainfall is modest, with 33 mm (1.3 in) spread over about 8 days, and a high average humidity of 87% makes for a crisp, damp atmosphere.

December Temperature in Umatilla

In December in Umatilla, the average temperature is 2°C (37°F). The maximum can reach 20°C (68°F), while the minimum can drop as low as -9°C (16°F). Be prepared for a wide range of temperatures during your travels.

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

The chart illustrates December temperature patterns in Umatilla, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Umatilla, December typically has an average temperature of 2°C (37°F), with highs reaching up to 20°C (68°F) and lows dropping to around -9°C (16°F).

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

December Precipitation in Umatilla

In Umatilla in December, the precipitation amount is 33 mm (1.3 in) during a span of 8 days.

December Precipitation Trends in Umatilla

The chart displays monthly precipitation patterns in Umatilla, 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 Umatilla, December typically receives around 33 mm (1.3 inches) of precipitation spread over approximately 8 days.

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

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Millimeters (mm) Inches (in)

December Humidity in Umatilla

In Umatilla in December, humidity is 87%. With an average temperature of 2°C (37°F), this humidity feels like an uncomfortable chill that seeps into your bones, making every step feel heavier and each breath a reminder of the dampness in the air, which can be quite challenging for traveling.

December Average Humidity in Umatilla

This chart illustrates the average monthly humidity levels in Umatilla, 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 Umatilla is approximately 87%, 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 Umatilla

In Umatilla in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Umatilla, you can visit Hourly UV Index in Umatilla.

Maximum UV Index Levels in Umatilla for December

The chart shows the monthly maximum UV Index (UVI) for Umatilla 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 Umatilla typically reaches 2, which falls under the low exposure category.

Data source: Umatilla 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 Umatilla Compares to Other Months

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

This table compares monthly weather conditions in Umatilla, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	2°C (36°F)	35 mm (1.4 inches)	86%	low
February Weather	3°C (37°F)	46 mm (1.8 inches)	86%	moderate
March Weather	8°C (46°F)	30 mm (1.2 inches)	85%	moderate
April Weather	13°C (55°F)	24 mm (0.9 inches)	83%	high
May Weather	18°C (65°F)	15 mm (0.6 inches)	77%	very high
June Weather	23°C (73°F)	8 mm (0.3 inches)	81%	very high
July Weather	27°C (81°F)	0 mm (0.0 inches)	76%	very high
August Weather	26°C (79°F)	4 mm (0.1 inches)	60%	very high
September Weather	20°C (69°F)	9 mm (0.4 inches)	58%	high
October Weather	12°C (54°F)	26 mm (1.0 inches)	75%	moderate
November Weather	6°C (43°F)	34 mm (1.3 inches)	85%	moderate
December Weather	2°C (37°F)	33 mm (1.3 inches)	87%	low