How turbulent is SEA-JFK typically?

Usually light, with two known rougher windows: over the mountain ranges and at the jet-stream crossing.

What is the best altitude to avoid turbulence on SEA-JFK?

Higher is usually calmer over the mountains. FL380 and above puts more distance between the aircraft and the strongest wave activity.

When is the best time of year to fly SEA-JFK?

Summer. Both the jet stream and mountain-wave winds are weaker between June and September.

What causes the turbulence on this route?

Jet-stream wind shear at cruise level, plus mountain waves generated when westerly winds cross high terrain.

Turbulence forecast SEA → JFK. Seattle to New York JFK. SkyBriefing.

Seattle to New York: what the SEA to JFK corridor looks like

Departure: Seattle Tacoma International Airport, Seattle, the United States
Arrival: John F. Kennedy International Airport, New York, the United States
Great-circle distance: 3,887 km (2,099 nm)
Typical airborne time: 5h 01m
Usual cruise levels: FL330 to FL390
Initial track: eastbound

Route overview

Seattle Tacoma International Airport (SEA) in Seattle, the United States, to John F. Kennedy International Airport (JFK) in New York, the United States, is a great-circle distance of 3,887 km, about 2,099 nautical miles. At typical jet cruise speeds, and with an allowance for climb, descent and approach, that works out to roughly 5h 01m of airborne time. The great-circle track leaves Seattle eastbound and spends most of the flight in mid latitude air.

Leaving Seattle

Seattle Tacoma sits between the Olympic and Cascade ranges on Puget Sound. Air funnelled between those ranges gives the climb out its character, particularly in winter storm season. The great-circle track leaves SEA eastbound, and the first waypoint band of the flight sits close to 45.7N 110.2W. On a sector of 5h 01m, the climb to cruise takes roughly the first twenty to twenty five minutes.

Jet stream plus mountain wave

The midpoint of the SEA to JFK track lies near 44.0N 98.0W, about 1,944 km from Seattle, which is where the corridor spends its longest continuous stretch at cruise level. Two things shape this corridor. Westerly wind flowing over the western North American ranges sets off mountain waves in the lower part of the cruise band, and further along the track the polar jet stream adds clear air turbulence in its shear zone. Crews normally see the mountain segment near one end of the flight and the jet segment in mid cruise, with calm air between them.

Cruise altitudes on this sector

Medium haul sectors typically level off between FL330 and FL390, with a single step climb once fuel burn has lightened the aircraft. Choice of level matters because turbulence is layered: a change of two or three thousand feet often puts the aircraft into calmer air, and that is one of the first adjustments a crew will request.

Arriving into New York

Arrivals into JFK are flown through one of the busiest terminal areas in the world, with level segments and frequent vectors. Sea air meeting land air along the Long Island coast is the common source of light chop on descent. Descent normally begins around 42.3N 85.9W, roughly 972 km before JFK, and takes about half an hour from cruise level to touchdown.

Seasonal pattern

Winter is the more active season here: both the jet stream and the westerly flow over the mountains are stronger between November and March, while July and August are typically the quietest months.

Flying this route with less worry

Turbulence on this corridor is a comfort issue rather than a safety one. Airliners are certified to handle loads well beyond anything the atmosphere produces here, crews are trained for it, and the seat belt sign is the tool that keeps the cabin settled. What this page adds is knowing in advance: the map and Calmness Score above use current WAFS forecast data for SEA to JFK, so you can see what to expect before you board.