Norman Y. Mineta San Jose International Airport turbulence forecast
San Jose, United States
SJC (San Jose, United States) sits at 37.36°N, 121.93°W, 62 ft elevation — coastal with the Rocky Mountains and Sierra Nevada nearby.
About SJC
Major airport serving San Jose, United States.
- Climate
- Mid-latitude maritime — variable, wind-driven weather
- Nearby terrain
- Rocky Mountains · Sierra Nevada
- Geography
- Coastal — marine-influenced airmass
What to expect on departures
Computed from SJC's geography and climate
San Jose 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 and Sierra Nevada sit upwind of SJC 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 SJC — afternoon thunderstorm cells are routed around but their wake turbulence and gust fronts can still affect arrivals and departures. SJC'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
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SJC turbulence FAQ
Is turbulence common on flights from SJC?
Norman Y. Mineta San Jose International Airport is best described as a jet-stream + mountain-wave corridor. San Jose sits squarely under the mid-latitude jet, north of which most long-haul corridors run.
When is turbulence worst for San Jose 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 San Jose affect turbulence?
Yes — the Rocky Mountains and Sierra Nevada 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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