Polar Vortex Explained

Stratosphere · 10 to 30 miles up

The polar vortex

It is not a storm and it is not new. It is a ring of wind high above the pole that forms every winter. When it breaks down, the weather far below can change for weeks.

See it in 3D Happening now

Happening now · updated automatically

The polar vortex is at a record low for the date

Measured. On November 9, 2026, the latest day in NASA's analysis, the wind circling the pole at the tracking level was 1.2 meters per second (3 mph) from the west. The average for that date is 28.4 meters per second (64 mph), and the lowest in earlier years was 12.4. Two weeks earlier the reading was 21.6. On November 5, 2026 it was 0.3. The lowest for that date in earlier years, in a record that starts in 1978, was 13.6.

Not reversed. For a major sudden stratospheric warming, the wind at this level has to reverse and blow from the east between November and March. In NASA's analysis it has not done so this season.

Forecast. NASA's forecast data runs through November 20, 2026 and ranges from −3.0 meters per second on November 11, 2026 to 20.6 on November 20, 2026. That includes an east wind from November 10 to 12, 2026. A forecast is not a measurement, and a reversal counts only once the analysis shows it.

−10 0 10 20 30 40 50 Sep 15 Oct 1 Oct 15 Nov 1 Nov 15 0: below this line the wind has reversed Nov 9: 1.2
  • Measured
  • Forecast
  • Average for the date
  • Usual range (middle 80% of years)
West-to-east wind at 60°N, 10 hPa, in meters per second. Positive is the normal winter direction, from the west. Data: NASA Ozone Watch.
Show the numbers
DateKindWind (m/s)Average for the dateLowest in earlier years
Oct 31Measured12.524.311.3
Nov 1Measured9.024.911.4
Nov 2Measured5.425.613.7
Nov 3Measured3.226.014.3
Nov 4Measured1.326.013.6
Nov 5Measured0.326.013.6
Nov 6Measured0.826.313.8
Nov 7Measured2.626.912.6
Nov 8Measured2.127.811.9
Nov 9Measured1.228.412.4
Nov 10Forecast−0.628.811.7
Nov 11Forecast−3.028.811.3
Nov 12Forecast−2.228.912.3
Nov 13Forecast1.629.210.8
Nov 14Forecast3.829.710.0
Nov 15Forecast4.629.97.7
Nov 16Forecast6.530.16.8
Nov 17Forecast8.930.56.6
Nov 18Forecast12.930.86.9
Nov 19Forecast17.030.27.0
Nov 20Forecast20.629.63.5

Updated automatically from NASA Ozone Watch's daily file, last checked November 12, 2026 UTC. The tracking level is 10 hectopascals, about 19 miles up, at 60°N. "Weaker" or "stronger than usual" means outside the middle 40% of earlier years for the same date (1978/1979 to 2025/2026), and "much" means outside the middle 80%.

Background · written November 10, 2026

November 2026: weaker than it had ever been that early in the season

What had been measured. At the level where scientists track the vortex, NASA's analysis showed the wind around the pole falling from about 22 meters per second (50 mph) on October 25 to 0.3 meters per second, under 1 mph, on November 5. The average for that date is about 26 meters per second (58 mph), and the previous low for the date, in a record that starts in 1978, was 13.6 meters per second (30 mph).1

What had not been confirmed. For this to count as a major sudden stratospheric warming, the wind has to reverse and blow from the east. Forecast data called for a brief, weak reversal around November 10 to 12. NASA's analyzed data, which ran through November 8 when this was written, still showed a west wind.1 A confirmed reversal would be the earliest major warming in records that go back to 1958. The earliest until then was in late November 1968.23 The reading above shows what the analysis found.

What forecasters said.

  • NOAA's Climate Prediction Center, November 6: "an unusually early sudden stratospheric warming (SSW) event is underway." It expected the event to be "relatively short-lived," in a pattern that "limits the availability of Arctic air masses across North America" into early December.4
  • The UK Met Office, November 4: the vortex "is already unusually stretched," but "there remains uncertainty over whether a major SSW will occur."5
  • Climatologist Judah Cohen, November 9: the event "should achieve major status" during the week, and he expected colder temperatures in North America in late November or early December.6

The complication. A strong El Niño was under way at the same time, and it pushes North American winters the other way, toward mild in the north. NOAA's forecasters wrote that some of the potential impacts of a sudden warming "compete with those from El Nino."7

"It looks like we're going to have a disruption. Where everything sets up is still in question."
Andrea Lopez Lang, University of Wisconsin-Madison, in Scientific American3

This background is not updated automatically. The reading above is.

87 mphthe average wind at its midwinter peak in late December, at the level where it is tracked1
About sixmajor breakdowns per decade in the Northern Hemisphere8
50 °Chow much the air over the pole can warm in a couple of days during one9

What it is

The Arctic polar vortex is a band of strong westerly winds that forms in the stratosphere, between about 10 and 30 miles above the North Pole, every winter.10 The winds blow from west to east, which is counterclockwise if you are looking down on the pole, and they circle a pool of cold air.11129 In winter the temperature inside usually drops below −78 °C (−109 °F).13

A good way to picture it is a spinning top. While it spins fast and tight, the cold air stays put over the pole. When something knocks it off balance, it wobbles, and cold air can end up far from where it started.3

Two things with one name

Part of the confusion around the polar vortex is that the name is used for two different things. Atmospheric scientists point out that there are "two quite different polar vortices in Earth's atmosphere," one in the troposphere and one in the stratosphere, and that the two are not directly connected.14

Stratospheric vortexTropospheric vortex
WhereFar above the weather, 10 to 30 miles up10In the weather layer
SizeWinds strongest near 60° latitude14Much larger; its edge is usually between 40° and 50°N14
WhenFall to spring only14All year14

When a forecast office says the polar vortex "ALWAYS exists near the poles," or describes it dropping south over Canada, it is using the name loosely, for the broad cold circulation lower down.1215 When a scientist says the polar vortex has split, they mean the one in the stratosphere. On this site, "polar vortex" means the stratospheric one unless it says otherwise.

10 km6 mi30 km19 mi50 km31 mi Polar vortexwinter only StratosphereTroposphere Tropopause Subtropical jetPolar jet Equator30°N60°NNorth Pole Warm airCold air
Schematic cross-section from the equator to the North Pole. The stratospheric polar vortex sits far above the jet streams and the weather.10

A winter-only feature

The vortex exists because of darkness. In fall, the pole stops receiving sunlight, and the polar stratosphere becomes very cold compared with the stratosphere over the tropics. That temperature contrast drives strong winds. The vortex strengthens through the winter and breaks down in spring when sunlight returns.1411

In NASA's long-term average, the wind at the tracking level turns westerly in late August, peaks on December 26 at about 39 meters per second (87 mph), and turns easterly again in mid-April. The strongest single day in that record reached about 75 meters per second (169 mph).1

North and south

Each pole has one. The Antarctic vortex is stronger, larger and longer-lasting than the Arctic one, and it is nearly always centered on the South Pole.13 The reason is geography. The Northern Hemisphere has bigger mountain ranges and sharper contrasts between land and sea, and these generate stronger atmospheric waves that travel upward and batter the Arctic vortex, leaving it weaker and more distorted.14

The cold inside the vortex is also a key ingredient of the Antarctic ozone hole. Clouds that form only in that extreme cold host reactions that free chlorine from CFCs into forms that rapidly destroy ozone.1413

How it breaks: sudden stratospheric warming

Every so often the vortex is knocked off balance. Scientists call the event a sudden stratospheric warming, or SSW: a large, rapid rise in temperature in the winter polar stratosphere.16 The air over the pole can warm by up to about 50 °C (90 °F) in a couple of days.9

The cause comes from below. Planet-sized waves in the atmosphere, generated mostly by air flowing over mountains and by the contrast between land and sea, travel upward from the weather layer and break in the stratosphere, like surf on a beach.1614

Minor or major?

A warming is called major when the wind at 60°N latitude and 10 hectopascals, about 30 km (19 miles) up, reverses from westerly to easterly between November and March.811 A warming without that reversal is called minor, though scientists acknowledge that the details of the definitions remain ambiguous.17 Major warmings happen about six times per decade in the Northern Hemisphere.82 In the Southern Hemisphere only one has ever been observed, in September 2002.14

State of the vortex
30°N60°N Polar vortexPolar jet stream Stretched vortexCold air Displaced vortexWarming LobeLobeWarmingCold air
Stable. The vortex is strong and centered on the pole. The polar jet stream beneath it tends to stay farther north and to meander less.10 Stretched. A lesser-known kind of disruption, in which the vortex is pulled into a long oval instead of breaking. One research group links it to extreme cold in parts of Asia and North America.18 Displaced. The vortex is pushed off the pole. This is one of the two classic forms of a sudden stratospheric warming.8 Split. The vortex breaks into two smaller lobes. In one widely used survey, 46% of major warmings were splits.8 Schematic, looking down on the North Pole with North America at the bottom. The dark blue shape is the vortex in the stratosphere. The bright line is the jet stream far below it. Lobe positions and the jet's path are illustrative.

What it means on the ground

A breakdown in the stratosphere does not reach the surface right away, and sometimes it does not reach it at all. When it does, the sequence looks like this:

  1. The change works downward

    The disturbed winds can propagate down into the weather layer over the following two to six weeks.5

  2. The jet stream buckles

    The polar jet often becomes extremely wavy. Warm air floods into the Arctic and polar air sinks toward the mid-latitudes.10

  3. The pattern locks in

    For about 60 days afterward, average surface pressure maps closely resemble the Arctic Oscillation pattern, usually in its negative phase.197

  4. Some regions turn cold

    Cold-air outbreaks become more frequent over North America and Eurasia, while Greenland and eastern Canada turn unusually warm.20

The cold is strongest over northern Europe and Asia, and it also shows up over the eastern United States.21 In the UK and northern Europe the typical result is a long spell of dry, cold weather.9

It loads the dice. It does not roll them.

About two-thirds of sudden warmings are followed by a negative phase of the North Atlantic Oscillation, the pressure pattern that dominates their effect at the surface.22 That leaves a third that are not. NOAA's stratosphere scientists put it this way: a major warming "loads the dice" for certain conditions, "but by no means guarantees them."21

It also works the other way. Cold-air outbreaks "can and often do occur in the absence of any detectable stratospheric influence."14 The sudden warming of February 2018 was followed by Europe's "Beast from the East." The one in January 2019 had no significant impact on UK weather.23

Events worth knowing

WhenWhat happened
Nov. 1968The earliest major warming on record until now, dated November 27 to 29 depending on the dataset.2
Jan. 1985A major warming in the first days of January. One of the most intense Arctic outbreaks of the 20th century hit the United States on January 18 to 22.224
Sept. 2002The first major warming ever observed in the Southern Hemisphere. It split the Antarctic ozone hole in two.25
Jan. 2009A vortex split on January 24, the strongest and most prolonged major warming on record at the time.262
Jan. 2014The cold outbreak that made "polar vortex" a household phrase. It was not a stratospheric event: no major warming happened that winter, and scientists say it "cannot be directly attributed to changes in the stratospheric vortex."1427
Feb. 2018A major warming on February 12, followed by the "Beast from the East" cold wave in the UK and Europe.2823
Jan. 2019A major warming at the start of January. An Arctic outbreak reached the U.S. Midwest on January 30 and 31, when Chicago hit −23 °F.229
Sept. 2019A rare warming over Antarctica. The ozone hole that year was the smallest since its discovery.3031
Jan.-Feb. 2021The winds reversed on January 5. The Texas freeze came on February 11 to 20. Whether the stratosphere caused the freeze is disputed: one study links it to a stretched vortex, and another finds that vortex stretching "had no discernible contribution to the record cold."2321833

Where a warming and a cold wave are listed together, the dates are given side by side. Unless a study is cited, that is not a claim that one caused the other.

Is climate change changing it?

Possibly, but the evidence points in different directions, and scientists disagree.

  • Studies that find a link. One found that weak-vortex states became more frequent in January and February over 37 years, followed by cold extremes in Eurasia.34 Another reported that stretched-vortex events have increased and tied them to changes in Arctic snow and sea ice.18
  • Studies that do not. A reconstruction back to 1850 shows swings from decade to decade but "no significant trend" in how often sudden warmings happen.22 Sixteen climate models agree that sea ice loss weakens the mid-latitude westerlies, but the effect is small, about 10% of the variation from one year to the next.35
  • The future. Climate models given four times as much carbon dioxide disagree even on whether sudden warmings become more or less frequent.36

NOAA's Amy Butler summed it up in 2021: "I don't think there is any convincing evidence of a long-term trend in the polar vortex."10 The related argument about the jet stream is covered under severe weather.

Three things people get wrong

Myth

"It's a storm heading for us."

It is not a feature at Earth's surface.12 It is a ring of wind 10 to 30 miles up. What reaches you is cold air steered by the jet stream.

Myth

"It's something new."

It forms every winter.10 The phrase took off after a cold wave in January 2014, which was not even caused by the stratospheric vortex.14

Myth

"A disrupted vortex means a brutal winter here."

Sometimes the vortex is disrupted and there are few, if any, effects on the weather at the surface.10

Sources

  1. NASA Ozone Watch. Daily zonal-mean zonal wind at 60°N and 10 hPa (data file), read November 10, 2026.
  2. NOAA Chemical Sciences Laboratory. SSW Compendium: table of major mid-winter sudden stratospheric warmings, updated September 2023.
  3. Scientific American. Mogensen, J. F., The polar vortex is about to go haywire, November 4, 2026.
  4. NOAA Climate Prediction Center. Week 3-4 outlook discussion (this address is overwritten with each new issue), issued November 6, 2026.
  5. UK Met Office. Deep dive: Could changes high above the Arctic influence the UK's weather?, November 4, 2026.
  6. Atmospheric and Environmental Research (AER). Cohen, J., Arctic Oscillation and Polar Vortex blog (this address is overwritten with each new post), post of November 9, 2026.
  7. NOAA Climate Prediction Center. 30-day outlook discussion (this address is overwritten with each new issue), issued October 31, 2026.
  8. Journal of Climate. Charlton and Polvani, A New Look at Stratospheric Sudden Warmings. Part I: Climatology and Modeling Benchmarks, 2007.
  9. UK Met Office. Sudden stratospheric warming.
  10. NOAA Climate.gov (archived). Understanding the Arctic polar vortex, March 5, 2021.
  11. NOAA Climate.gov Polar Vortex Blog (archived). Welcome to the Polar Vortex Blog!, December 5, 2023.
  12. NOAA National Weather Service. What is the Polar Vortex?.
  13. NASA Ozone Watch. Polar vortex.
  14. Bulletin of the American Meteorological Society. Waugh, Sobel and Polvani, What Is the Polar Vortex and How Does It Influence Weather?, 2017.
  15. NOAA National Weather Service, Fort Worth. February 2021 winter event.
  16. Reviews of Geophysics. Baldwin et al., Sudden Stratospheric Warmings, 2021.
  17. Bulletin of the American Meteorological Society. Butler et al., Defining Sudden Stratospheric Warmings, 2015.
  18. Science. Cohen et al., Linking Arctic variability and change with extreme winter weather in the United States, 2021.
  19. Science. Baldwin and Dunkerton, Stratospheric Harbingers of Anomalous Weather Regimes, 2001.
  20. Earth System Science Data. Butler et al., A sudden stratospheric warming compendium, 2017.
  21. NOAA Climate.gov Polar Vortex Blog (archived). But what does a polar vortex breakdown look like down here?, February 29, 2024.
  22. Journal of Geophysical Research: Atmospheres. Domeisen, Estimating the Frequency of Sudden Stratospheric Warming Events From Surface Observations of the North Atlantic Oscillation, 2019.
  23. UK Met Office. Has there been a Sudden Stratospheric Warming – and what does that mean for our weather?, January 26, 2023.
  24. NOAA National Weather Service, Wilmington NC. January 1985 Record-breaking Cold.
  25. Journal of the Atmospheric Sciences. Newman and Nash, The Unusual Southern Hemisphere Stratosphere Winter of 2002, 2005.
  26. Geophysical Research Letters. Manney et al., Aura Microwave Limb Sounder observations of dynamics and transport during the record-breaking 2009 Arctic stratospheric major warming, 2009.
  27. NOAA Climate.gov (archived). Wobbly polar vortex triggers extreme cold air outbreak, January 8, 2014.
  28. Geophysical Research Letters. Karpechko et al., Predicting Sudden Stratospheric Warming 2018 and Its Climate Impacts With a Multimodel Ensemble, 2018.
  29. NOAA National Weather Service, Chicago. Record cold January 30-31, 2019.
  30. Bulletin of the American Meteorological Society. Lim et al., The 2019 Southern Hemisphere Stratospheric Polar Vortex Weakening and Its Impacts, 2021.
  31. NASA. 2019 Ozone Hole is the Smallest on Record Since Its Discovery, October 21, 2019.
  32. NOAA National Centers for Environmental Information. The Great Texas Freeze: February 11-20, 2021, February 24, 2023.
  33. Nature Communications. Davis et al., Limited surface impacts of the January 2021 sudden stratospheric warming, 2022.
  34. Bulletin of the American Meteorological Society. Kretschmer et al., More-Persistent Weak Stratospheric Polar Vortex States Linked to Cold Extremes, 2018.
  35. Nature Communications. Smith et al., Robust but weak winter atmospheric circulation response to future Arctic sea ice loss, 2022.
  36. Journal of Geophysical Research: Atmospheres. Ayarzagüena et al., Uncertainty in the Response of Sudden Stratospheric Warmings and Stratosphere-Troposphere Coupling to Quadrupled CO2 Concentrations in CMIP6 Models, 2020.

Last updated November 12, 2026