Seattle Weather in December
🇺🇸 United States
North America › 🇺🇸 United States › Seattle
Updated: March 2026
Is December a Good Time to Visit Seattle?
December is a fair time to visit Seattle (4/10). Average highs of 15°C and 1 sunshine hours daily make conditions workable, though not exceptional. December suits travellers visiting for indoor culture, food, and architecture rather than outdoor activities. Pack accordingly for 7 potential rain days. January offers a similar profile at lower hotel rates if dates are flexible. The main practical note: Seattle's popular sites are busiest between 10am and 3pm regardless of season. Arriving at opening time or after 4pm makes a significant difference to the experience. Planning tips: most accommodation categories have availability, and last-minute deals are common. The quieter streets and shorter queues can make this a genuinely enjoyable time to visit for the right type of traveller. Budget-conscious visitors will find the best value of the year in this period.
Seattle in December rewards travelers with average highs of 15°C and overnight lows around 6°C. Expect around 7 rainy days, making it one of the drier periods in the city. With 1 daily sunshine hours on average, conditions are cool and bracing, well suited for active days on foot.
15°C
Avg High
6°C
Avg Low
7 days
Rain Days
1h
Sunshine
65%
Humidity
Temperature in Seattle in December
The 9°C day-night temperature range is typical for continental climates: a light jacket in the morning that you shed by midday and need again after sunset. Humidity averages 65%, which is comfortable for most visitors. On warmer days, lighter fabrics help with the mild stickiness in the afternoon. The UV index of 1 is low, meaning sun exposure is minimal concern and sunscreen is largely optional. Wind averages 15 km/h, light enough to be refreshing on warm days but noticeable in open coastal areas or elevated viewpoints. In Fahrenheit: 59°F average high, 43°F overnight low. Data sourced from Open-Meteo ERA5 climate reanalysis (1991–2020 normals).
Temperature in December
Monthly Precipitation (mm)
What to Wear in Seattle in December
Packing for Seattle in December means dressing for 15°C days and 6°C evenings. A mid-weight jacket over a sweater handles 15°C daytime temperatures; the combination stays comfortable all day without overheating. Evening temperatures settle at 6°C, a modest 9°C drop that a light cardigan or denim jacket covers. Comfortable walking trainers are the versatile choice for both outdoor sightseeing and indoor venues.
Local tip: Layers are more practical than a single heavy garment in Seattle. The day-to-evening temperature shift rewards packing a versatile mid-layer you can add or remove as conditions change.
Events in Seattle in December
December has no major festivals or public holidays in Seattle, which is one of its practical advantages for independent travellers. Attractions run at lower capacity than during peak event periods, queues are shorter, and accommodation is easier to find without needing to book many months in advance. Local restaurants, markets, and transport operate at a relaxed pace, making this an ideal time for visitors who prefer a more authentic, unhurried experience of everyday city life rather than large crowds drawn in by a single major headline event.
What to Pack for Seattle in December
Based on 15°C average highs and 7 rainy days
- Warm jacket (down or fleece)
- Merino wool base layer (regulates temperature and resists odour)
- Sweaters and lined trousers
- Scarf and lightweight gloves
- Comfortable walking shoes (a second pair lets the first air out overnight)
- Universal travel adapter
- Small day pack for city exploration
- Reusable water bottle
Best Activities in Seattle in December
- Explore the old town's cobblestone backstreetsMorning (9-11am)At 15°C, conditions are pleasant for unhurried exploration on foot
- Visit hilltop viewpoints for panoramic city viewsLate afternoon (4-6pm)Low sun angle creates dramatic light for photography while temperatures remain comfortable
- Bicycle rental for a half-day city circuitMid-morning startMild 15°C temperatures are ideal for extended cycling without excessive effort
- Boat tour of the river, bay, or canal networkLate morning departureComfortable weather makes open-deck boats viable without wind-chill concerns
- Afternoon in a world-class museum or galleryAfternoon (2-5pm)Pairs well with outdoor morning activities and provides a mid-day rest from sightseeing
- Coffee-house or traditional cafe culture experienceMid-morning or post-lunchA cultural ritual in this region that rewards slow appreciation regardless of weather
- Evening live music, theatre, or opera performanceEvening shows typically at 7-9pmConsistent evening temperatures make getting to and from evening venues comfortable
- Visit the main botanical garden or city park at seasonal peakYear-round; best light in morningDecember brings distinct seasonal changes to public green spaces worth exploring
- Warm up with traditional hot dishes: local stew, fondue, or braised specialities at a neighbourhood restaurantLunch (12-2pm) or dinner (7-9pm)Cold-weather cuisine is a genuine cultural experience and the best local restaurants serve their heartiest dishes in cooler months
Why is Seattle mild in December?
In December, Seattle feels the full influence of the continental polar air mass, which dominates mid-latitude interiors during winter. Cold, dry air from the north suppresses temperatures to 15°C during the day, dropping further to 6°C at night when radiative cooling is greatest. Precipitation tends to be low, as the cold air holds little moisture. Climate data: Open-Meteo ERA5 (1991–2020).
Sunshine Hours
The average number of hours per day with direct sunlight. Calculated from satellite measurements. Days with more than 7 hours of sunshine are ideal for outdoor activities. Under 3 hours means overcast conditions dominate.
UV Index
A scale from 0-11+ measuring ultraviolet radiation intensity. UV 0-2: Minimal risk. UV 3-5: Moderate -- wear sunscreen. UV 6-7: High -- hat and SPF 30+ essential. UV 8-10: Very High -- limit midday exposure. UV 11+: Extreme -- seek shade between 10am-4pm.
Rain Days
A rain day is counted when precipitation exceeds 0.1mm. This threshold captures even light drizzle. Unlike total rainfall in mm, rain days tells you how often you might need an umbrella, which is useful for planning outdoor activities.
Humidity
Relative humidity as a percentage. Below 40%: Dry -- skin and throat may feel parched. 40-60%: Comfortable -- ideal for most people. 60-80%: Sticky -- light, breathable fabrics recommended. Above 80%: Muggy -- heat feels more intense; quick-dry clothing is essential.
Frequently Asked Questions: Seattle in December
December ranks 12th sunniest of the year in Seattle, with an average 1 daily sunshine hours. The driest months are May, June, and July. June is the hottest month (29°C avg high); December is the coolest (15°C). From here, temperatures rise 1°C into January. Compared to last month (November: 16°C high, 6 rain days), December is cooler and wetter. December is one of the least sunny months, but that often means lower prices and fewer fellow tourists.
Year-Round Climate
Plan Your Trip to Seattle
Data Sources for Seattle
Climate normals represent 30-year averages (1991-2020). Individual years may vary.