doodlejets.

WHAT THE METEOROLOGISTS SAY

A river of wind
above the clouds.

You cannot see it, but it steers our weather.

Around 5 to 7 miles up, the jet stream blows from west to east. The Met Office says its position is often the driving force behind the weather we get in the UK, from winter storms to a dull July.

Check the jet Read the short answer
High wispy cirrus clouds streaking across a deep blue sky above green British countryside, swept along by strong winds aloft
AI-generated image, not a photograph of a real person or place.
01 Strong in winter02 North in summer03 Wavy means stuckSmall shifts, big weather

THE SHORT ANSWER

Where the jet sits,
the weather follows.

The jet stream works like a conveyor belt high overhead.
It moves, strengthens and sometimes stalls weather systems.

STORMS

It deepens the lows

Over an area of low pressure the jet stream can act like a vacuum cleaner, drawing air out of the top. The pressure falls further and the weather turns stormier.

Check the jet

SEASONS

Winter over us, summer to the north

In winter the temperature contrast is bigger, so the jet is stronger and often sits over the UK. In summer it usually shifts north, giving calmer, drier weather.

See the numbers

FLIGHTS

A tailwind or a headwind

The jet flows at about the height transatlantic aircraft fly. Flying with it can cut flight times and fuel; flying against it can bring delays.

Reading the forecast

A QUICK JET CHECK

Where is the jet
stream today?

Pick where the jet stream is in the forecast to see the kind of weather the Met Office links with it. The bar shows how unsettled the UK weather tends to be.

A general guide based on Met Office explainers. Real weather depends on many factors, so always use the actual forecast and warnings.

Jet check

Choose a jet stream position
Strong and straight over the UKWet and windy

This is the typical winter pattern. A strong jet over the UK drives low pressure systems across, which is why the colder months tend to be wetter and windier.

Shifted south of the UKCool and showery

In summer 2024 the jet was over or south of the UK, which the Met Office said brought cooler air and unseasonable wind and rain.

Shifted north of the UKChance of warmth

With the jet further north, warmer air can drift up from the south. The Met Office notes this is the usual set-up for warm summer weather, though not a guarantee.

Wavy, with a blocking highStuck and settled

A strongly meandering jet can leave high pressure parked overhead for weeks, as in spring 2025: mostly dry and sunny, while the edges of the high stay wet and windy.

Sources: Met Office, What is the jet stream?; Met Office blog posts of 16 July 2024 and 7 May 2025.

TWO NUMBERS WORTH KNOWING

High up,
and very fast.

One figure on how high the jet stream blows,
one on how fast its core can get.

HEIGHT · MET OFFICE

Height of the jet stream

5–7 miles up

The Met Office describes the jet stream as a core of strong winds around 5 to 7 miles above the Earth's surface. NOAA gives a typical height of about 30,000 feet.

SPEED · NOAA

Top speeds in the core

275+ mph

NOAA says jet streams can reach speeds of more than 275 mph (442 km/h). The Met Office says the jet stream can reach speeds of over 200 mph.

NOAA describes two main jets in each hemisphere: the polar jet between about 50° and 60° latitude and the subtropical jet near 30°. Both follow the boundaries between hot and cold air.

A passenger jet far up in a clear blue sky leaving a long white trail, seen from the ground through a gap in clouds
AI-generated image, not a photograph of a real person or place.

FOUR THINGS TO LISTEN FOR

Make sense of
the jet stream chat.

Forecasters often mention the jet stream when the weather changes. These four ideas help you follow what they mean.

  1. Ask where it sitsOver or south of the UK usually means unsettled weather; to the north opens the door to warmer, drier spells.
  2. Expect it stronger in winterThe bigger temperature contrast between equator and poles makes the winter jet stronger, bringing wetter and windier weather.
  3. Watch for big wavesA buckled, amplified jet can slow weather systems or park a blocking high overhead, so the same weather lasts for days or weeks.
  4. Check the warnings, not the jetThe jet explains the pattern; the forecast and weather warnings tell you what will actually happen where you live.

WHY IT EXISTS

Hot meets cold,
and the Earth spins.

The jet stream exists because of the temperature difference between the equator and the poles. In the northern hemisphere cold polar air lies to the north of it and warmer air to the south, and that contrast drives the high-level winds.

The Earth's rotation turns the flow eastwards. NOAA explains that air moving away from the equator keeps its eastward momentum while the ground beneath it moves more slowly, so the wind runs from west to east. This is the Coriolis effect.

Dark storm clouds and heavy rain sweeping across a windswept British coastline with waves breaking on the shore
AI-generated image, not a photograph of a real person or place.

QUESTIONS PEOPLE ASK

Frequently asked

What is the jet stream?

The Met Office describes it as a core of strong winds around 5 to 7 miles above the Earth's surface, blowing from west to east. NOAA calls jet streams relatively narrow bands of strong wind in the upper atmosphere, or rivers of air.

Is there more than one jet stream?

Yes. NOAA describes a polar jet between about 50° and 60° latitude and a subtropical jet around 30°, in both hemispheres. They can meander, split and even disappear for a while.

Why is UK weather wetter in winter?

In winter the temperature difference between the equator and the poles is larger, so the jet stream is stronger and often flows over the UK. The Met Office says this is why we tend to see wetter, windier weather then.

Is there a Caribbean jet stream?

No. The Met Office says a Caribbean jet stream is not a meteorological term. Warm spells come from where the air mass is drawn from, such as the Azores, helped by small shifts in the jet stream.

Does the jet stream affect my flight?

It can. The Met Office says it flows at about the height of transatlantic aircraft: flying with it saves time and fuel, flying against it costs both, and it can bring turbulence where the wind changes speed.

SOURCES

Where the facts come from

Each figure on this page comes from the sources below. Check them for the full detail and context.

  1. Met Office: What is the jet stream?
  2. Met Office blog: What is the jet stream and how does it affect our weather? (28 May 2025)
  3. Met Office blog: Weather trends, blocking highs and the amplified jet stream (7 May 2025)
  4. Met Office blog: What's happened to summer so far? (16 July 2024)
  5. NOAA JetStream: The Jet Stream