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Answer: The polar vortex is a large area of low pressure and cold air surrounding both of Earth's poles. It always exists near the poles, weakening in summer and strengthening in winter. 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.

How it sends cold air south

Many times during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream. When the Arctic vortex is strong and stable, the polar jet stream shifts northward and the coldest polar air stays in the Arctic. When the vortex weakens, shifts, or splits, the jet stream often becomes extremely wavy, allowing warm air to flood into the Arctic and polar air to sink into the mid-latitudes.

Sudden stratospheric warmings

The vortex is occasionally knocked off kilter when strong atmospheric waves break upward into the stratosphere. It may wobble, slide off the pole, split into several lobes, or temporarily reverse direction. These disruptions share a spike in polar stratosphere temperatures, which is why they're called sudden stratospheric warmings.

What it is not

• Polar vortexes are not something new; the term has only recently been popularized.
• It is not a feature that exists at the Earth's surface. Forecasters examine it by looking at conditions tens of thousands of feet up.
• It is not confined to the United States: portions of Europe and Asia also experience cold surges connected to it.

Claims

• id: C1 claim: The polar vortex always exists near the poles. source: S1 evidence: "It ALWAYS exists near the poles, but weakens in summer and strengthens in winter."
• id: C2 claim: The Arctic polar vortex occurs in the stratosphere in winter. source: S2 evidence: "The Arctic polar vortex occurs in the stratosphere in the winter."
• id: C3 claim: Vortex disruptions often lead to cold air outbreaks in the mid-latitudes. source: S2 evidence: "Disruptions of the vortex often lead to cold air outbreaks in the mid-latitudes."

Sources

• [S1] What is the Polar Vortex?. NOAA. https://www.weather.gov/safety/cold-polar-vortex . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Understanding the Arctic polar vortex. NOAA. https://www.climate.gov/news-features/understanding-climate/understanding-arctic-polar-vortex . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_atam2tat,
  author = {{iinventedlight}},
  title = {{The polar vortex: what it is and what it is not}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/polar-vortex/},
  note = {Permanent ID iil:note:atam2tat. License: CC-BY-4.0.},
}

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