Seattle · December
Run in the midday.
Cold: average high 45°F, low 37°F. Layering becomes the workout. Humidity averages 84% — the limiting factor on most runs. Expect 21 rain days — plan around the radar. Cold mornings warm into runnable midday hours — the windows around noon catch the warmest temperatures.
Avg high / low
45° / 37°F
Humidity
84%
Rain days
21/mo
Wind
12 mph
What December feels like in Seattle
Sunrise
08:50
Mid-month average
Sunset
17:20
Mid-month average
Time-of-day breakdown
Morning
Coolest, driest air of the day. The window before sunrise is the most reliable comfortable hour.
Midday
Mild but UV and traffic peak. Workable if you don't mind shifting your pace.
Evening
Warm and runnable. Crowded routes but the air's typically calm.
What to wear running in Seattle in December
The kit for December in Seattle: a long-sleeve or light jacket for the first mile, a water-resistant cap or jacket on standby.
December vs the surrounding months
vs November
-5° avg high
+2 rain days
Seattle in November →
December
45°F avg high
21 rain days
Best: midday
vs January
-1° avg high
+2 rain days
Seattle in January →
Frequently Asked Questions
What is the best time of day to run in Seattle in December?+
Midday. Cold mornings warm into runnable midday hours — the windows around noon catch the warmest temperatures.
What's the average temperature in Seattle in December?+
Average high 45°F, average low 37°F.
How does December compare to surrounding months in Seattle?+
Compared to November (avg high 50°F), December is cooler. Compared to January (avg high 47°F), December is cooler.
Does it rain often in Seattle in December?+
Expect about 21 measurable rain days in December, on average.