Winter weather: Snow and ice in unincorporated King County

The County plows and sands up to 583 miles of designated snow and ice routes. We work together with public safety officials to determine which roads are on each snow and ice route.

Our snow and ice routes are categorized by number. The routes are plowed and sanded in priority order. Category 1 and 2 routes contain main arterials and major roads. These routes are treated first because emergency responders rely on them. Once our Category 1 and 2 routes are taken care of, we move on to plow and sand our Category 3, 4, and 5 snow and ice routes.

We work with first responders to clear roads that are outside of our designated snow routes when directed by 9-1-1.

Category 1:

• High-volume arterial roads that provide regional connections between communities and main highways
• Lifeline emergency routes, routes to hospitals and other emergency services
• Transit snow routes

At times, snow may accumulate faster than our plows can keep up with. Crews will continue to re-plow Category 1 routes until they are all clear before moving on to Category 2 routes.

Category 2:

• Main thoroughfares and roads that lead to densely populated areas and state highways
• Minor collector roads that serve densely populated areas

Some Category 2 routes may be delayed or not plowed and treated until all Category 1 routes are fully clear.

Category 3:

• Main roads that connect towns and large subdivisions with cities
• Roads connecting Category 1 and Category 2 routes.

Categories 4 and 5:

• Residential roads in lower and upper elevations that connect neighborhoods to each other.

In most cases, communities should not expect roads other than designated snow routes to be plowed and sanded in any type of storm.

There are 1500 miles of road in Unincorporated King County. We make the best use of our limited resources by plowing and sanding one-third of our road system. Our high-volume roads that deliver traffic to and from the highway, lifeline emergency routes, transit routes and minor collector roads that serve densely populated areas. There are 583 miles of designated snow and ice routes in the system. Map of 2022-23 snow routes PDF 2MB

We do our best to clear designated snow and ice routes in priority order. Sometimes unforeseen issues arise that slow down our progress. For example, we may need to redirect crews off a snowplowing route to clear a fallen tree from a different road. At times, emergency responders ask us to clear other areas so that fire trucks and ambulances can respond to a 9-1-1 incident. Last, but not least, snow plowing may be delayed due to equipment breakdowns.

During a storm we are not able to take requests to plow or sand any road within our designated snow and ice routes. At times, it may be possible to honor a request once the storm has passed. It depends on how severe the storm is. Residents may call our 24/7 Road Helpline to request snowplowing or sanding within a designated snow and ice route.

In most cases, communities should not expect roads other than designated snow and ice routes to be plowed and sanded in any type of storm. If your area is not on a designated snow route, be prepared to wait up to several days and, when possible, avoid driving, in severe weather. If you need life-safety emergency access plowing, or are medically vulnerable and in need of treatment, call 9-1-1.

You can check our Winter Weather Response Map to see where our plows have recently cleared away snow. It could take several days for crews to clear and sand all 583 miles of designated snow and ice routes.

If your road is on a designated snow route but has not been plowed, you may call or email our 24/7 Road Helpline to find out the status of your route.

Yes. View our Winter Weather Response Map to track recently plowed areas. The information on the map is posted approximately 15 minutes after the road has been plowed. The time delay helps prevent drivers from tailgating our snowplows -which is very dangerous!

If you need life-safety emergency access plowing, or are medically vulnerable, call 9-1-1.

Make sure to check the snow route map  PDF 2MB to see if your road is a designated snow route. We plow and sand designated snow and ice routes by category. Category 1 is plowed first, then Category 2, and so on. It could take up to three days to plow and treat Categories 1 and 2, depending on how much snow we get. This means, if your road is on a Category 3, 4 or 5 route, it could take several days until crews are able to treat your road.

Community members who do not live on a designated snow and ice route should prepare in advance for the possibility of being snowed in for up to seven days during a major winter storm.

Sometimes the only way crews can reach the next designated snow route on their list is to plow a side street or section of road that lies between two routes. This side street or section may not be on a designated snow route; however, crews plow it if it is the most direct way to continue their work.

There are times when we need to travel on lower category roads to reach the higher category road. As a result, there may be occasions where a section of a lower category snow route may be plowed or receive treatment when drivers need to drive and clear that section to reach a higher category snow route. Another reason for half-road treatment is when 9-1-1 responders request us to plow or treat a road for emergency response.

A countywide snow and ice event occurs when snow and ice response crews are needed in most or all areas of unincorporated King County at the same time.

Countywide events often require us to dispatch all of our available snow response resources to plow and sand as many miles of designated snow routes as possible.

A localized snow and ice event occurs when snow and ice response crews are needed in one or two areas of unincorporated King County at the same time.

At times, snow may accumulate faster than our plows can keep up with; however, county crews will plow and sand the Category 1 routes throughout the snow event.

Category 1:

• High-volume arterial roads that provide regional connections between communities and main highways
• Lifeline emergency routes, routes to hospitals and other emergency services
• Transit snow routes

Category 2, Category 3 and Category 4 routes will be plowed and sanded in descending order after Category 1 routes.

You can check our Winter Weather Response Map to see where our plows have recently cleared away snow.

The county does not have the resources to plow all 1500 miles of road in unincorporated King County.

We will work with first responders to clear roads that are outside of our designated snow routes when directed by 9-1-1. However, in most cases, communities should not expect roads other than designated snow routes to be plowed and sanded in any type of storm.

No. Residents are responsible for clearing snow from driveways.

The Washington State Department of Transportation (WSDOT) manages state highways and freeways. Check WSDOT's snow and ice page for news and information.

For snow removal in cities and towns in King County, visit the city or town's website (here's a list of links) and look for snow and ice information or plow routes and maps.

If needed, snowplows will be pulled off routes to help emergency vehicles gain access into neighborhoods for life and safety emergency response. Emergency snowplowing is coordinated through first responders and the Office of Emergency Management.

King County employs year-round licensed and trained road maintenance crews that are experienced at operating snow and ice removal equipment. Crew members actively roam unincorporated King County roadways around the clock to monitor and respond to winter weather such as ice and snow, flooding and downed trees.

King County crews from other departments such as the Department of Natural Resources and Parks are also trained to drive plows and help clear and sand roads within our designated snow route area when needed.

No. The County cannot authorize private community members, residents or private snow removal contractors to plow public roads. Plowing public roads is dangerous and difficult work. Our county crews are licensed and trained to handle the hazards of extreme weather conditions, out-of-control vehicles on slippery roads, abandoned vehicles, children playing near or in the road, and steep terrain.

Please do not attempt to plow a county road.

Residents or contractors who plow a public road risk significant personal liability if someone is hurt or killed, or if property is damaged. Other jurisdictions such as Pierce and Snohomish counties also do not allow private residents or private contractors to plow public roads.

King County uses private contractors (when available) to assist during very large, countywide winter storms. These private contractors augment county crews and work under the direction of King County snow and ice removal supervisors.

No. It is illegal for anyone other than King County to employ or contract with contractors that are licensed to use any type of equipment that could be used for snow removal or road treatment.

Drivers should always use caution and expect slippery conditions when driving during winter weather.

Ice can form sooner on the decks of bridges and overpasses before it does on the roadway because air can circulate both above and below the surface of the elevated roadway, causing the pavement temperature to drop more rapidly. Ice can also form in shaded areas.

Black ice, also known as “glare ice” or “clear ice,” is a thin coating of glazed ice on the road. Black ice is not actually black. Instead, it is transparent, allowing you to see the asphalt road surface through it. Black ice often occurs along with wet roads, making it hard to see and especially hazardous for driving or walking.

Crews pre-treat county roads with anti-icer when the conditions are right. The surface must be dry and the pavement temperature must be between 20 and 30 degrees Fahrenheit for anti-icer to work. If the road is wet, the anti-icer substance would dilute too fast and fail to work. If the road is too cold, the anti-icer solution won’t stick to the roadway.

King County uses an anti-icer solution called “calcium chloride with boost.” The calcium chloride is salt; “boost” is a solution made of bio-solids such as egg whites and beet juice which helps reduce corrosion on infrastructure.

The calcium chloride (salt) adheres to the surface helping prevent ice from forming. Salt and water can cause rust on metal vehicles and equipment. Boost provides a chemical reaction that prevents rust from forming when the anti-icer solution comes into contact with vehicles and snow-removal gear.

Anti-icer is different from de-icer. Anti-icer is applied to bare, dry roads. De-icer is applied to roads that have compacted snow and ice on the surface. De-icing uses large amounts of chemicals. King County does not use de-icer.

County crews spread salt, sand or a mix of salt and sand over plowed and unplowed roadways to help make slick surfaces less slippery.

Dry salt is most effective after the snow has accumulated about an inch and the temperature is 20 degrees Fahrenheit or higher. If the temperature is below 20 degrees, crews use a mixture of pre-wetted salt and sand to break up ice and increase traction. Pre-wetted salt and sand sticks to cold, icy surfaces better and jump-starts the ice melting process.