Aircraft take-off and land facing into the prevailing winds. SEA operates in a south-flow or north-flow condition depending upon the direction of the prevailing winds.
When the winds are from the south, aircraft will depart the airport in a southerly direction and arriving aircraft will approach from the north. This operation occurs most commonly during the cooler, cloudier months of the year. The airport is in south-flow operations approximately 65 percent of the year.
When winds are from the north, aircraft will depart from the airport in a northerly direction and arriving aircraft will approach from the south. This operation occurs most commonly during the warmer, sunnier periods of the year.
