When the weather outside is frightful … and you’re worried your trip won’t be so delightful, here’s everything you need to know about Sea-Tac International Airport’s winter weather operations. We don’t want to go so far as to say “Let It Snow” but if it does, we’ll be ready.
Sea-Tac International Airport is the eighth busiest airport in the country, averaging 1,200 to 1,300 flights per day, so even a little bit of bad weather can have a big impact on flight operations. The Sea-Tac Airport team works all year and around the clock to prepare for, respond to, and communicate with you about inclement weather, whether it’s rain, snow, sleet, smoke, or fog.
In a normal season, Sea-Tac Airport budgets about 4,000 hours for snow removal. In the last 11 seasons, the airport has seen an average of six inches of snow. The biggest season was in 2008-2009 when almost 24 inches of snow fell at the airport.
Bad weather is rarely a surprise to the airport team. Before you even know it’s coming, the Sea-Tac team has been getting ready and planning for the worst. Here’s how.
Watch the Weather
Sea-Tac Airport has access to weather information through NOAA and the National Weather Service 24 hours a day, 7 days a week, 365 days a year. There’s a weather sensor right at the airport for accurate readings and the National Weather Service provides the airport with custom reports.
Control the Snow
Before winter weather begins, the airport opens the Snow Control Center, a central management facility for all airport snow and ice control activities. It facilitates communications and speedy decision making in a larger snow and ice event.
Assemble the Snow Team
The snow team is made up of 99 people — 74 members of the Port and Sea-Tac teams who are trained in snow removal, and 25 mechanics standing by to make sure the equipment works. By the time bad weather hits, the snow team has already been preparing. Months before, they begin checking the equipment, stocking up supplies like sand and de-icer fluid in the snow shed, practicing with the equipment, and getting ready for the inevitable.
Get the Equipment Ready
Sea-Tac Airport has more than 45 pieces of equipment on hand for snow and ice maintenance including:
- Two friction testers to measure stopping distance for the runways
- Three sander/plows
- Seven high-speed plows
- Nine plow and broom combination units — state-of-the-art trucks with a 24-foot plow that’s as long as a semi truck
- Four de-icing trucks for roadways (three 75-foot-wide booms, one 45-foot boom)
- 11 additional sander, plow and chemical trucks dedicated for landside maintenance.
- Pickup trucks with sanders and plows
- Seven high-speed plows
- Five snow blowers
- 10 high-speed brooms
- Walk-behind Snow blowers
- Lots of snow shovels and brooms and team members ready to work
Practice Makes Perfect
Every November all members of the snow team go through recurrent training. The ops staff review the snow and ice control plan, and re-familiarize themselves with the snow alert levels. The maintenance staff reviews the plans, but they also go out in the snowplows and do a mock snow removal event on the runway.
Stock Up on Supplies
The airport stocks up the snow shed with runway de-icer and sand. The following supplies are on hand and ready for deployment:
- 300 tons of roadside sand
- 350 tons of runway sand
- 70 tons of dry chemical (used with sand)
- Runway de-icer
- De-icing chemicals to be spread by hand on stairways around the terminal
When Mother Nature gets cranky, winter weather operations kick into high gear. During a weather event here’s what’s happening behind the scenes.
De-Ice the Aircraft
The fluids used for de-icing airfields are different than the substances used to de-ice airplanes. Chemicals are sprayed on the wings and fuselage of a plane to prevent icing. Each of the airlines are responsible for providing de-icing fluids and applying it to their planes.
Remove Snow on the Runway
On the airfield, Sea-Tac Airport handles all common use areas and manages de-icing of the runways, taxiways, ramp areas in and around the gates and cargo area, and adjacent airport roadways. Airlines are responsible for clearing ice and snow from their specific gates.
Snow removal on the runways takes place with several snow plows stretched out at an angle with snow brooms following.
- It can take 30-45 minutes to clear a runway, and the Snow Team works as quickly as possible so aircraft can continue to arrive and depart. The current operations goal is under 30 minutes.
- The Port of Seattle maintains a stock of special sand that meets FAA specifications and can used for airplanes without doing damage to aircraft. Sand is provided to airline partners at no charge.
Snow removal happens in the following order:
Priority 1: Runways, taxi lanes, and taxiways
Priority 2: Hardstands (when an airplane is parked and passengers are transported by bus to the airports. Sea-Tac uses this operation to get passengers on and off planes more quickly rather than waiting for a gate during busy times)
Priority 3: Bagwell ramps, vehicle service roadways, sloped roads
Video: Meet the snow team and see their equipment
De-Ice the Runway
Anti-icing occurs before snowfall when temperatures reach 33-34 degrees. Anti-icing fluid works to stop ice from bonding to the concrete. The runways have embedded temperature monitors that allow staff to apply anti-icing fluid only when necessary in order to conserve the supply. The airport uses biodegradable potassium acetate as a liquid runway anti-icer. A solid runway deicer, sodium acetate, also is used at lower temperatures. On-site tanks store 62,000 gallons of anti-icing fluid and supplies are restocked during the winter to maintain an acceptable stockpile.
In case you’re wondering about the environmental impact, the de-icer solution used on the ground does not harm streams. The airplane de-icing solution is collected through an industrial wastewater system and is sent for secondary treatment at a King county Treatment Plant.
- Average fluid used per season: 36,000 gallons
- Total anti-icing fluid used 2008-2009 season: over 120,000 gallons
Remove Snow around the Terminal
Sea-Tac Airport is responsible for maintaining the terminal and facilities, including:
- Keeping the terminal area free of snow and ice
- Maintaining the parking garage and roads and drives, including Starling Road, Air Cargo Road to the Employee Parking Lot and the Airport Expressway just north of the return-to-terminal loop
- Sanding the roadways (with a different type of sand then is used for planes)
- During heavy snowfalls of two inches or more and accumulating, the Port hires two contractors to remove and collect snow piles. One for the north side of the ramp, and one for the south end.
Transport Employees and Travelers Safely
The Port monitors the roadways and facilities around the airport for snow and ice. This includes airport ground transportation, public parking, and employee parking. And the buses between the terminal and the employee parking lots and rental car facilities.
- The eighth floor of the parking garage has sensors and is closed during snow or in low temperatures
- The helixes in parking garages are monitored hourly for snow and ice
- The goal is passenger waiting times of less than five minutes at rental car facility
In case you’re curious, here are a few stats about ground transport operations:
- 426 trips per day between the terminal and rental car facility
- Buses carry 10,000 people per day on 29 buses
- With staffing of 58 bus drivers, 13 support staff, 12 bus mechanics, and 8 staff who fuel and clean buses
Deal Fog and Low Visibility
Flights can be delayed in the event of low visibility like snow, fog, and even smoke from forest fires.
Video: Watch a Facebook Live Checking In video with Airport Director of Operations Mike Ehl on how the airport operates in heavy weather conditions like snow and fog.
Here are a few terms you may hear during weather operations.
A gate hold is when aircraft are required to stay at the gate until air traffic has a spot for them to depart and is managed by the Federal Aviation Administrator or the Port. For example, an airplane can be held at the gate to apply de-icing solution.
What Is a Ground Stop?
A ground stop can happen with low or limited visibility and departures are restricted from taking off until arrivals are safely on the ground.
On a typical sunny day, the airport could see 50 airplane arrivals per hour. On a hazy or foggy day, it could decrease to 28 arrivals per hour. A ground stop is a situation when aircraft cannot come to the airport due to snow or fog (or other conditions like smoke) and they are being held in another airport like Portland or San Francisco.
Once airport landings are approved, the next task is to get airplanes in the sky sequenced correctly and start letting them back in. “Metering” begins, which means maintaining a level of separation between planes appropriate for the conditions, and letting them land. Every flight is different depending upon departure time, destination, and international or domestic. So don’t assume that all flights are delayed — check with your airline for the most up to date information.
Video: See a Facebook Live Video about the basics of air traffic control and what happens in a low visibility situation.
There are several tools you can use to find out what is happening during a weather incident and year-round.
Sea-Tac Airport Home Page
If there is a weather event or other incident, check the Sea-Tac Airport home page for a colored alert bar or an Incident Advisory graphic. Link
Flight Aware’s Flight Cancellations Page
This site tracks daily by airport delays and cancellations. To track Sea-Tac flight status, input KSEA into the Filter all Stats by airport box. Link
Sea-Tac Flight Information Online
This is the same information seen on the in-terminal flight information displays and comes from the airlines. You can use this page to check the status of specific flights, or delays to or from another airport. For example, to check delays or cancellations for flights to Chicago, select the Chicago airport under Arrivals and Departures, then leave the airline blank.
Or, check with your airline about your flight status.
Weather Conditions at Sea-Tac Airport
Get the latest conditions and forecast from NOAA/The National Weather Service station.
Download the Sea-Tac App for your iOS and Android platforms to get updates on your flight and Checkpoint Wait Times.
Sea-Tac Airport Social Media
Sea-Tac Airport Text Alerts
Sign up to be notified of a weather incident or receive alerts during peak travel periods. Text the word UPDATE to 206-347-8045.
Sound Transit Alerts
View service alerts or sign up for email and text alerts.