December in Washington State presents a varied climatological picture. Western Washington typically experiences cool temperatures, abundant rainfall, and occasional lowland snow. The Cascade Mountains accumulate significant snowfall, creating a winter wonderland for skiing and other snow sports. Eastern Washington, characterized by a drier climate, sees colder temperatures, less precipitation, and greater snowfall potential in higher elevations. This diverse range of conditions within the state during the final month of the year creates unique opportunities for residents and visitors alike.
Understanding typical weather patterns for this period is crucial for several reasons. It informs safe travel practices, particularly over mountain passes. It influences the choice of recreational activities, from snowshoeing in the mountains to storm watching on the coast. Historically, December weather has played a significant role in agriculture, impacting late-season harvests and preparations for the next growing season. Accurate weather predictions are also vital for water resource management, as snowpack accumulation in the mountains is a major source of the state’s water supply.
Further exploration of this topic will delve into specific regional climates, average temperatures and precipitation levels, historical weather data, and the impact of climate change on December weather patterns in Washington State. This information will provide a more detailed understanding of the diverse conditions experienced across the state during this time of year.
1. Coastal Rain
Coastal rain plays a defining role in Washington State’s December weather. The state’s western coastline, facing the Pacific Ocean, experiences a significant increase in precipitation during this month. This phenomenon results from prevailing westerly winds carrying moisture-laden air masses from the Pacific. As these air masses encounter the Olympic and Cascade mountain ranges, they are forced upwards, cool, and condense, resulting in abundant rainfall. The intensity and frequency of these rain events contribute significantly to the overall character of December weather in western Washington. Locations like Forks, Aberdeen, and Quinault consistently rank among the nation’s wettest during December, receiving several inches of rain. This coastal rain influences regional ecosystems, river flows, and local economies.
The impacts of this substantial rainfall are multifaceted. Increased river and stream flows can lead to flooding in low-lying areas, posing challenges to infrastructure and requiring careful monitoring by local authorities. The saturated ground also increases the risk of landslides, particularly in hilly or mountainous terrain. Conversely, this rainfall contributes significantly to the region’s water resources, recharging aquifers and reservoirs vital for supplying water throughout the year. Understanding the typical rainfall patterns allows for better planning and mitigation of potential hazards, ensuring the safety and well-being of coastal communities.
In summary, coastal rain is an integral component of Washington State’s December weather. Its influence extends beyond simple precipitation, shaping landscapes, impacting ecosystems, and posing challenges that require careful management. Recognizing the patterns and potential consequences of this increased rainfall is critical for both residents and visitors, enabling them to prepare for and navigate the unique conditions of the Pacific Northwest during December.
2. Mountain Snow
Mountain snow is a defining characteristic of Washington State’s December weather, particularly in the Cascade and Olympic Mountain ranges. Significant snowfall accumulations reshape the landscape, impacting transportation, recreation, and the state’s water resources. Understanding the dynamics of mountain snow is crucial for navigating the challenges and opportunities presented by this essential aspect of December weather.
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Transportation Impacts
Heavy snowfall significantly impacts mountain pass travel. Interstate 90 (Snoqualmie Pass), US Highway 2 (Stevens Pass), and other major routes frequently experience closures or require tire chains due to heavy snow and ice. This necessitates careful planning for travelers, potentially causing delays or requiring alternate routes. The Washington State Department of Transportation (WSDOT) provides real-time updates on road conditions and closures, a crucial resource during the winter months.
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Recreational Opportunities
Abundant mountain snow creates a winter wonderland for recreational activities. Ski resorts such as Crystal Mountain, Stevens Pass, and Mount Baker attract skiers and snowboarders from across the region and beyond. Snowshoeing, cross-country skiing, and snowmobiling also become popular pursuits. The influx of winter recreation enthusiasts contributes significantly to local economies, highlighting the positive economic impact of mountain snow.
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Water Resource Management
December snowfall contributes significantly to the state’s snowpack, which serves as a natural reservoir. The gradual melting of this snowpack throughout the spring and summer provides essential water resources for agriculture, hydroelectric power generation, and urban consumption. Monitoring snowpack levels is critical for water resource management, ensuring equitable distribution and mitigating potential shortages during drier months.
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Avalanche Risk
Heavy snowfall in the mountains increases the risk of avalanches, posing a significant hazard to backcountry recreationists. Organizations like the Northwest Avalanche Center provide crucial avalanche forecasts and safety information, empowering individuals to make informed decisions and minimize risks. Understanding avalanche safety protocols and carrying appropriate equipment are essential for anyone venturing into the backcountry during periods of heavy snowfall.
In conclusion, mountain snow profoundly shapes Washington State’s December weather. Its influence on transportation, recreation, water resources, and avalanche hazards necessitates careful planning and awareness. Recognizing the complex interplay of these factors is essential for safely and effectively navigating the unique conditions of Washington’s mountains during December.
3. Eastern Cold
Eastern Washington experiences significantly colder temperatures during December compared to the western part of the state. This stark contrast results from the Cascade Range, which acts as a barrier, blocking the moderating influence of the Pacific Ocean. The resulting “cold air damming” effect traps cold, dense air east of the mountains, leading to frigid conditions. Understanding the dynamics of this Eastern cold is crucial for comprehending the broader picture of Washington State’s December weather.
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Temperature Extremes
Eastern Washington experiences significantly lower temperatures during December, often dipping well below freezing. Cities like Spokane, Pullman, and Omak regularly record overnight lows in the single digits or even below zero Fahrenheit. These extreme temperatures necessitate specific preparations for residents, including protecting pipes from freezing, ensuring adequate home insulation, and taking precautions against hypothermia and frostbite.
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Precipitation Patterns
While Eastern Washington is generally drier than the west side, December can still bring significant snowfall, particularly in higher elevations. The Palouse region, known for its rolling hills, often experiences heavy snowfall, impacting transportation and agriculture. The lower temperatures combined with snowfall create hazardous driving conditions, emphasizing the need for winter tires and cautious driving practices.
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Impact on Agriculture
The Eastern cold has significant implications for agriculture. Winter wheat, a major crop in the region, enters dormancy during December, relying on snow cover for insulation and protection from extreme cold. Orchards and vineyards also require specific cold weather protection measures to prevent damage to fruit trees and grapevines. The timing and severity of cold snaps can significantly impact agricultural yields and economic viability.
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Influence of Arctic Air Masses
Occasionally, outbreaks of arctic air from Canada plunge southward into Eastern Washington, exacerbating the already cold conditions. These arctic air masses can bring extremely low temperatures, strong winds, and blowing snow, creating blizzard-like conditions and further impacting transportation, infrastructure, and daily life. Monitoring weather forecasts for these potential arctic intrusions is crucial for preparedness.
The Eastern cold significantly contributes to the diverse weather landscape experienced across Washington State during December. Its influence on temperature extremes, precipitation patterns, agriculture, and the potential impact of arctic air masses creates a unique set of challenges and opportunities for residents. Understanding these dynamics provides valuable insights into the complexities of Washington State’s December weather and emphasizes the importance of preparedness for the diverse conditions across the state. This awareness allows for more informed decision-making regarding travel, recreation, and overall winter safety in Eastern Washington.
4. Variable Temperatures
Variable temperatures are a hallmark of Washington State’s December weather. The state’s diverse geography, ranging from coastal regions to high mountains and arid plains, contributes to significant temperature fluctuations within short distances and across short time spans. The Cascade Range plays a crucial role, creating distinct climate zones. Western Washington experiences milder temperatures due to the moderating influence of the Pacific Ocean, while eastern Washington endures colder, continental conditions. This east-west temperature differential is a defining characteristic of the state’s climate.
Diurnal temperature swings can also be substantial, particularly in eastern Washington. Clear skies and dry air allow for rapid radiative cooling overnight, leading to significant drops in temperature. Conversely, sunny days can bring relatively mild temperatures, even in December. For example, Spokane might experience a daytime high of 35F and an overnight low of 15F, a 20-degree swing. Coastal areas experience less diurnal variation due to the thermal inertia of the Pacific Ocean. These variable temperatures necessitate adaptable clothing strategies and underscore the importance of accurate weather forecasting for planning outdoor activities.
Understanding the variable temperatures characteristic of Washington State’s December weather is crucial for several reasons. It informs decisions regarding appropriate attire for outdoor activities, impacting comfort and safety. It influences travel plans, particularly over mountain passes, where conditions can change rapidly. It impacts agricultural practices, affecting livestock management and crop protection. Recognizing the dynamic nature of December temperatures allows residents and visitors to prepare effectively, ensuring safety and maximizing enjoyment of the diverse environments within Washington State during the winter months.
5. Reduced Daylight
Reduced daylight is a defining characteristic of December in Washington State, significantly influencing weather patterns and daily life. The state’s high latitude results in shorter days and longer nights during the winter solstice period. This decrease in solar radiation directly impacts temperatures, contributing to colder conditions. The reduced daylight also influences visibility, impacting transportation and outdoor activities. Understanding the implications of reduced daylight is crucial for navigating Washington’s December weather.
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Impact on Temperatures
Shorter days and less direct sunlight lead to decreased solar radiation, contributing significantly to lower temperatures statewide. With less solar energy to warm the land and air, temperatures drop, particularly overnight. This effect is amplified in eastern Washington, where the continental climate leads to greater temperature extremes. The reduced solar input plays a crucial role in establishing the overall colder conditions prevalent throughout December.
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Influence on Visibility
Reduced daylight hours, combined with frequent cloud cover and precipitation, often result in limited visibility. Fog, particularly in river valleys and coastal areas, can further reduce visibility, creating hazardous driving conditions. These factors necessitate increased caution while driving and emphasize the importance of using headlights even during daylight hours. Reduced visibility also impacts outdoor recreational activities, requiring extra precautions for safety.
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Effects on Mood and Behavior
The decrease in daylight hours can influence human mood and behavior. Seasonal Affective Disorder (SAD), a type of depression related to changes in seasons, can be exacerbated by reduced daylight. The lack of sunlight can disrupt circadian rhythms, impacting sleep patterns and energy levels. Awareness of these potential effects is important for maintaining well-being during the winter months.
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Impact on Energy Consumption
Reduced daylight hours lead to increased reliance on artificial lighting, contributing to higher energy consumption. Homes and businesses utilize more electricity for lighting, impacting both individual energy bills and the overall energy grid. This increased demand underscores the importance of energy conservation practices during the winter months.
Reduced daylight is an integral component of Washington State’s December weather. Its influence on temperatures, visibility, human behavior, and energy consumption has broad-reaching implications. Understanding these interconnected factors provides valuable context for navigating the unique challenges and opportunities presented by Washington’s December climate. This awareness empowers residents and visitors to make informed decisions regarding travel, recreation, and overall well-being during the shortest days of the year.
6. Frequent Cloud Cover
Frequent cloud cover is a prominent feature of Washington State’s December weather, particularly in western Washington. This prevalence of clouds significantly influences temperature, precipitation, and overall atmospheric conditions. Understanding the role of cloud cover is crucial for comprehending the complexities of Washington’s December climate.
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Temperature Moderation
Cloud cover acts as insulation, moderating temperature fluctuations. During the day, clouds reflect incoming solar radiation, preventing significant warming. At night, they trap outgoing heat, preventing rapid cooling. This moderating effect reduces the diurnal temperature range, resulting in milder daytime highs and warmer overnight lows compared to clear-sky conditions. This influence is particularly noticeable in coastal regions.
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Enhanced Precipitation
Frequent cloud cover is directly linked to increased precipitation in western Washington during December. Clouds are essentially condensed water vapor, and their prevalence increases the likelihood of rainfall. The orographic lift effect, where air masses are forced upwards over mountain ranges, further enhances cloud formation and precipitation along the windward slopes of the Cascades and Olympics. This contributes to the region’s reputation for significant rainfall during December.
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Reduced Solar Radiation
Persistent cloud cover significantly reduces the amount of solar radiation reaching the surface. This decrease in sunlight impacts plant growth and can influence human mood and behavior. Reduced solar radiation also contributes to the overall gray and overcast conditions often associated with December weather in western Washington. This characteristic “cloudiness” distinguishes the region’s climate during the winter months.
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Influence on Visibility
Frequent cloud cover, often combined with fog and precipitation, can significantly reduce visibility. This poses challenges for transportation, particularly aviation and marine navigation. Reduced visibility necessitates increased caution while driving, requiring the use of headlights and slower speeds. These conditions underscore the importance of staying informed about weather conditions and adjusting travel plans accordingly.
Frequent cloud cover is an integral component of Washington State’s December weather. Its influence on temperature moderation, precipitation patterns, solar radiation, and visibility significantly shapes the overall character of the season. Recognizing the multifaceted role of cloud cover provides valuable insights into the complexities of Washington’s December climate, contributing to a more comprehensive understanding of the state’s weather dynamics.
7. Potential for Flooding
December in Washington State carries a significant potential for flooding, particularly in western Washington and along rivers fed by snowmelt from the Cascades. Abundant rainfall, combined with saturated ground and potential for rapid snowmelt due to warmer temperatures or rain-on-snow events, creates conditions conducive to flooding. Understanding these factors is crucial for mitigating the risks associated with December flooding.
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Coastal Flooding
Coastal areas are particularly vulnerable to flooding during December. High tides combined with storm surges driven by strong onshore winds can inundate low-lying areas. Coastal communities such as Aberdeen, Hoquiam, and Long Beach face heightened flood risks during periods of intense storms. Infrastructure damage, erosion, and disruption to transportation networks are potential consequences of coastal flooding.
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Riverine Flooding
Rivers throughout western Washington are prone to flooding in December due to heavy rainfall. The Chehalis, Skagit, Snohomish, and Cowlitz rivers have historically experienced significant flooding events during this period. Saturated ground reduces the ability of the soil to absorb rainfall, leading to increased runoff and swollen rivers. This poses risks to communities located in floodplains and necessitates flood control measures, including levees and early warning systems.
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Rain-on-Snow Events
A significant concern in December is the potential for rain-on-snow events, particularly in the foothills and lower elevations of the Cascades. Warm rain falling on existing snowpack can cause rapid melting, leading to a surge of water into rivers and streams. This can exacerbate riverine flooding and trigger landslides in steep terrain. Monitoring snowpack levels and forecasting rain events are crucial for predicting and mitigating the risks associated with rain-on-snow flooding.
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Urban Flooding
Urban areas, with their extensive impervious surfaces, are susceptible to flooding during periods of heavy rainfall. Storm drains can become overwhelmed, leading to street flooding and backups into basements. Proper drainage maintenance and stormwater management practices are crucial for minimizing the impacts of urban flooding. Public awareness campaigns encouraging residents to clear storm drains and avoid driving through flooded areas can also contribute to flood mitigation efforts.
The potential for flooding is a significant consideration related to Washington State’s December weather. Coastal flooding, riverine flooding, rain-on-snow events, and urban flooding all pose risks to communities and infrastructure. Understanding these diverse flood mechanisms and implementing appropriate mitigation strategies are crucial for ensuring safety and minimizing the disruptive impacts of flooding during December in Washington State. Preparedness measures, informed by accurate weather forecasting and effective communication, are essential for navigating the challenges presented by this potential hazard.
8. Pass Closures
Pass closures are a frequent consequence of Washington State’s December weather, particularly affecting the Cascade and Olympic Mountain ranges. Heavy snowfall, combined with high winds, freezing rain, and avalanche risk, often necessitates the closure of mountain passes for safety reasons. These closures significantly impact interstate travel, freight transport, and regional connectivity, highlighting the direct link between weather conditions and transportation infrastructure.
Several major mountain passes, including Snoqualmie Pass (I-90), Stevens Pass (US-2), and White Pass (US-12), are particularly susceptible to winter weather closures. The Washington State Department of Transportation (WSDOT) actively monitors weather conditions and road safety, implementing closures when travel becomes hazardous. These closures can range from a few hours to several days, depending on the severity and duration of the storm. The economic impacts of pass closures can be substantial, disrupting supply chains, impacting tourism, and affecting the daily lives of commuters. For instance, the closure of Snoqualmie Pass, a major east-west artery, can effectively isolate communities east of the Cascades, disrupting access to essential goods and services.
Understanding the potential for pass closures is critical for anyone traveling in or through Washington State during December. Checking WSDOT’s real-time road conditions and pass reports is essential for trip planning. Carrying emergency supplies, including extra food, water, and warm clothing, is crucial in case of unexpected delays or closures. Flexibility and alternative route planning are essential strategies for navigating the challenges posed by pass closures during the winter months. Recognizing this inherent connection between December weather and transportation safety is paramount for responsible travel within Washington State.
Frequently Asked Questions about Washington State Weather in December
This FAQ section addresses common inquiries regarding weather conditions in Washington State during December. Understanding these aspects is crucial for safe travel, effective planning, and overall preparedness for the diverse conditions experienced across the state during this time of year.
Question 1: How much snow does Washington State typically receive in December?
Snowfall varies significantly across the state. Western Washington lowlands typically receive little to no snow, while mountain areas can accumulate several feet. Eastern Washington experiences greater snowfall potential, particularly in the higher elevations.
Question 2: Are mountain passes often closed in December?
Yes, mountain passes, including Snoqualmie Pass, Stevens Pass, and White Pass, are frequently closed in December due to heavy snowfall, high winds, or avalanche risk. Checking pass conditions before travel is essential.
Question 3: What are typical temperatures in December?
Western Washington experiences milder temperatures, generally hovering just above freezing. Eastern Washington experiences much colder temperatures, often well below freezing.
Question 4: How much rain does western Washington receive in December?
Western Washington, particularly the coastal regions, receives significant rainfall in December, often exceeding several inches. This contributes to saturated ground conditions and potential flooding.
Question 5: What should one pack for a December trip to Washington State?
Packing layers is crucial due to variable temperatures. Waterproof outerwear, sturdy footwear, and warm accessories are essential. If traveling to mountainous regions, consider packing chains and emergency supplies.
Question 6: What are some popular December activities in Washington State?
Popular activities include skiing, snowboarding, snowshoeing, and other winter sports in the mountains. Coastal areas offer storm watching and exploring the rainforests. Holiday festivals and events occur throughout the state.
Careful planning and preparation are crucial for navigating the diverse weather conditions experienced across Washington State during December. Consulting reliable weather forecasts and transportation updates is strongly advised.
For further in-depth information, continue to the next section, which provides detailed regional climate breakdowns.
Tips for Navigating Washington State Weather in December
Careful preparation is essential for navigating the diverse weather conditions experienced across Washington State during December. The following tips offer guidance for safe travel, informed decision-making, and overall preparedness.
Tip 1: Check Road Conditions Before Traveling, Especially Over Mountain Passes. Mountain passes are frequently closed due to snow, ice, or avalanche risk. Consulting the Washington State Department of Transportation (WSDOT) website for real-time updates is crucial.
Tip 2: Pack for Variable Temperatures and Precipitation. Layered clothing is essential, allowing for adjustments to fluctuating conditions. Waterproof outerwear, sturdy footwear, and warm accessories like hats, gloves, and scarves are recommended.
Tip 3: Carry Emergency Supplies in Vehicles. A winter car kit containing extra food, water, blankets, a flashlight, and a first-aid kit is crucial, especially for mountain travel. Tire chains should also be included and their use practiced before encountering snowy conditions.
Tip 4: Be Aware of Potential Flooding, Particularly in Western Washington. Monitor weather forecasts for flood warnings and avoid driving through flooded areas. Stay informed about local evacuation routes and procedures.
Tip 5: Allow Extra Time for Travel. Winter weather conditions can cause significant delays. Planning for extra travel time reduces stress and allows for flexibility in case of unexpected road closures or detours.
Tip 6: Be Prepared for Reduced Visibility. Frequent cloud cover, fog, and precipitation can limit visibility. Drive cautiously, use headlights, and be aware of potential hazards on roadways.
Tip 7: Stay Informed About Weather Forecasts. Regularly checking weather updates from reliable sources provides crucial information for making informed decisions about travel and outdoor activities.
Tip 8: Consider the Impact of Reduced Daylight on Mood and Energy Levels. Seasonal Affective Disorder (SAD) can be exacerbated by reduced daylight. Maintaining a healthy lifestyle, including regular exercise and a balanced diet, can help mitigate these effects.
Adhering to these tips enhances safety and preparedness for the varied weather conditions encountered in Washington State during December. Proactive planning contributes significantly to a more enjoyable and secure experience.
Following these tips will better prepare residents and visitors for the unique challenges and opportunities presented by Washington State’s December weather. The next section concludes this comprehensive overview.
Conclusion
Washington State’s December weather presents a complex tapestry of conditions, ranging from coastal rain and mountain snow to eastern cold and variable temperatures. Frequent cloud cover and reduced daylight further shape the character of this month. Potential hazards, including flooding and pass closures, necessitate preparedness and careful consideration of travel plans. Understanding these diverse elements is crucial for safe navigation and informed decision-making during December.
December weather significantly influences the state’s transportation infrastructure, recreational opportunities, and overall economic activity. Its impact on agriculture and water resources underscores the importance of accurate forecasting and proactive planning. Recognizing the dynamic nature of December weather in Washington State is essential for both residents and visitors, enabling informed choices and fostering resilience in the face of variable conditions.
