Aircraft primarily take-off and land facing into the prevailing winds. Sea-Tac operates in a south-flow or north-flow condition, depending upon the direction of the prevailing winds.
Winds from the south
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% of the year.
Winds from the north
When winds are from the north, aircraft will depart 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.
