December in washington

In Washington State, the weather in December marks the height of the winter season, with colder temperatures and an increase in precipitation. Western Washington, including cities like Seattle and Olympia, typically experiences daytime highs ranging from 45°F to 50°F (7°C to 10°C), while nighttime lows drop to around 35°F to 40°F (2°C to 4°C). In contrast, Eastern Washington, in areas like Spokane and the Tri-Cities, sees even colder conditions, with daytime highs averaging 30°F to 40°F (-1°C to 4°C) and nighttime lows often plunging into the low 20s or teens (-6°C to -2°C).

December is one of the wettest months of the year in Western Washington. Seattle averages about 5.4 inches (137 mm) of rainfall, and snow is possible but less common due to the region’s maritime influence. Eastern Washington, though colder, is drier, with Spokane receiving around 2 inches (51 mm) of precipitation, much of it in the form of snow.

Air quality is generally not a major concern in December, as the wildfire season has ended and smoke from fires is no longer an issue. However, in some Eastern Washington valleys, temperature inversions can trap air pollutants close to the ground, leading to occasional periods of poor air quality during the winter months.