What causes turbulence? The 5 everyday reasons the ride gets bumpy
Turbulence is caused by moving air: the jet stream, mountains, warm rising air, storms and the wake of other planes. Here is what each one feels like and when to expect it on your flight.
Turbulence sounds mysterious, but the causes are surprisingly ordinary: air moving at different speeds, temperatures and directions. Once you know the five main sources, most bumps on a flight become predictable, and a lot less scary.
1. The jet stream and wind shear (clear-air turbulence)
High above the weather, around 30,000 to 40,000 feet, there are fast rivers of wind called jet streams, sometimes over 150 knots. Where the speed or direction of the wind changes quickly with height, the air rolls and tumbles, a bit like water where a fast current meets a slow one. Planes crossing that boundary feel clear-air turbulence, bumps out of a blue sky with no cloud to warn you.
It's most common on long routes that cross jet streams, such as the North Atlantic or the North Pacific, and more frequent in winter, when jet streams are strongest. More in Clear-air turbulence explained.
2. Mountains (mountain waves)
When strong wind blows across a mountain range, the air goes up and over and then ripples downstream in waves, like water flowing over a rock in a stream. Flights over the Rockies, the Alps or the Andes on a windy day often feel a few minutes of chop because of this.
3. Warm rising air (thermal turbulence)
On sunny days, the ground heats up unevenly and bubbles of warm air rise from it. Flying through them at low altitude feels like a gentle up-and-down, mostly during climb and descent on hot afternoons. It's the reason summer landings in warm places can be a little bouncy, and why it often smooths out once you're above the clouds.
4. Storm clouds (convective turbulence)
Inside and near big thunderstorm clouds (cumulonimbus), air rises and falls strongly. This is the turbulence pilots take most seriously, which is exactly why they don't fly through thunderstorms. Weather radar in the nose shows storm cells far ahead, and pilots route around them, sometimes with a few bumps on the edges. If you see the plane turning before a storm, that's the system working.
5. Wake turbulence
Every aircraft leaves swirling air behind its wings. Air traffic control spaces planes so they don't fly into each other's wake, especially behind large jets during takeoff and landing. Occasionally you might feel a short, sharp wobble from crossing an old wake at cruise. It's brief and harmless.
When are you most likely to feel turbulence?
| Phase of flight | Typical cause | What it feels like |
|---|---|---|
| Climb and descent | Warm rising air, wind near the ground, clouds | Gentle bounces, usually over within minutes |
| Cruise over oceans | Jet stream edges | Steady chop that can come and go for a while |
| Over mountain ranges | Mountain waves | A few minutes of bumps |
| Near storms | Convective air | Bumps on the edges as pilots route around |
How pilots deal with each type
- Before the flight, the crew and the airline's dispatchers study forecast turbulence and storms along the route.
- During the flight, pilots get live reports from aircraft ahead and ask air traffic control for a smoother altitude. Often a change of 2,000 to 4,000 feet is all it takes.
- In the bumps, they slow to the aircraft's recommended turbulence speed and switch on the seatbelt sign. The autopilot often stays on and holds the plane steady.
Can you predict turbulence on your own flight?
Partly. Weather models show where the jet stream is strong, where winds change sharply with height and where storms may build. Our free turbulence forecast uses those models to show where bumps are likely along your route, minute by minute. It can't promise a smooth or bumpy ride, but it tells you what's normal for your trip.
Frequently asked questions
Why is there turbulence when the sky is clear?
Clear-air turbulence comes from wind shear, usually near the jet stream, where there's no cloud to make it visible. It's the same moving air as any other turbulence, just without a visual warning.
Why are some routes bumpier than others?
Routes that cross the jet stream, mountain ranges or areas with frequent storms tend to have more turbulence. Westbound transatlantic flights, for example, often cross the jet stream head on.
Is turbulence worse at night?
Not necessarily. Thermal turbulence from the sun is weaker at night, so climb and descent can feel smoother. Clear-air turbulence at altitude doesn't care about the time of day.
Does the size of the plane matter?
Yes for comfort, no for safety. Larger aircraft are heavier and respond less to the same air movement, so the ride usually feels smoother.
