Seattle Tacoma International Airport turbulence forecast
Seattle, United States
SEA (Seattle, United States) sits at 47.45°N, 122.31°W, 433 ft elevation — coastal with the Rocky Mountains nearby.
About SEA
Major airport serving Seattle, United States.
- Climate
- Mid-latitude maritime — variable, wind-driven weather
- Nearby terrain
- Rocky Mountains
- Geography
- Coastal — marine-influenced airmass
What to expect on departures
Computed from SEA's geography and climate
Seattle sits squarely under the mid-latitude jet, north of which most long-haul corridors run. Clear-air turbulence (CAT) at cruise is the most common source of bumps on departures from here, especially during December–February when the jet is at its strongest. The Rocky Mountains sit upwind of SEA on prevailing flow days, generating mountain-wave turbulence that can extend several hundred kilometres downwind at cruise level. The lee-wave risk is highest when December–February winds at FL300 cross the Rocky Mountains at near-perpendicular angles. Warm-season convection (June–August) drives the dominant turbulence pattern from SEA — afternoon thunderstorm cells are routed around but their wake turbulence and gust fronts can still affect arrivals and departures. SEA's coastal position means departures often transit from the cool marine boundary layer into warmer continental air within minutes of takeoff — a brief but reliable bumpy transition on warm-season afternoons when the sea breeze is set up.
Climbout notes
Standard Instrument Departures (SIDs) often route around terrain; on strong-wind days, low-level turbulence in the lee of the hills is common in the first few thousand feet.
Seasonal pattern
Winter (December–February) brings the strongest jet-stream activity — that's when long-haul departures most often log clear-air turbulence at cruise. Summer (June–August) is peak thunderstorm season — convective turbulence is the dominant warm-season risk. Mountain-wave activity near the Rocky Mountains peaks in the cold season when upper-level winds blow hardest across the range.
- Peak turbulence
- November–February (strong jet)
- Typically calmest
- May–September
Departing from SEA?
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Popular routes from SEA
SEA turbulence FAQ
Is turbulence common on flights from SEA?
Seattle Tacoma International Airport is best described as a jet-stream + mountain-wave corridor. Seattle sits squarely under the mid-latitude jet, north of which most long-haul corridors run.
When is turbulence worst for Seattle flights?
Winter (December–February) brings the strongest jet-stream activity — that's when long-haul departures most often log clear-air turbulence at cruise. Peak turbulence window: November–February (strong jet). Typically calmest: May–September.
Does the terrain around Seattle affect turbulence?
Yes — the Rocky Mountains lie close enough to generate mountain-wave turbulence on days with strong upper-level winds. These waves can propagate hundreds of kilometres downwind, so they sometimes affect cruise even after you've left the immediate area.
How accurate are Turbcast forecasts?
We combine live NOAA Aviation Weather Center data (PIREPs, SIGMETs, AIRMETs) with physics-based Ellrod and Richardson-number calculations derived from Open-Meteo pressure-level wind and temperature data. If a source is unavailable for a waypoint we show an em dash rather than invent a number.
Articles
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