Polar Vortex
The polar vortex is a large area of low pressure and cold air surrounding each of Earth's poles. It always exists, weakening in summer and strengthening in winter. During Northern Hemisphere winter it often expands, sending Arctic air south with the jet stream and producing cold outbreaks across the United States.
Common Misconceptions
- It is not new. The polar vortex has always existed, and only the name became popular recently. Similar cold outbreaks occurred in 1977, 1982, 1985, and 1989.
- It is not at ground level. Forecasters track it tens of thousands of feet up, and the extreme cold at the surface is an effect associated with it.
- It is not a storm that arrives and leaves. It is a permanent feature near the poles that sometimes stretches far enough south to affect the middle latitudes.
Related Terms
Jet Stream
A jet stream is a relatively narrow band of strong wind in the upper atmosphere, typically around 30,000 feet, that blows from west to east. The polar jet sits between 50° and 60° latitude and the subtropical jet near 30°. Jet streams follow the boundaries between cold and warm air and steer the storm systems below them.
Wind Chill
Wind chill is how cold the air feels on exposed skin once wind is taken into account. Wind strips heat from the body faster than still air does, so the wind chill temperature is lower than the air temperature. At 0°F with a 15 mph wind, the wind chill is -19°F, and exposed skin can freeze in 30 minutes.
Alberta Clipper
A fast-moving low-pressure system that originates near Alberta, Canada, and tracks southeast across the northern United States. Clippers typically bring light snow (1-4 inches) followed by bitter cold and gusty winds.
Blizzard
A blizzard is a storm with sustained winds or frequent gusts of 35 mph or more and falling or blowing snow that frequently reduces visibility to below a quarter mile, lasting 3 hours or longer. The National Weather Service definition has no snowfall or temperature requirement: wind and visibility make a blizzard.
El Niño and La Niña
El Niño and La Niña are the warm and cool phases of a recurring climate pattern in the tropical Pacific called the El Niño-Southern Oscillation (ENSO). During El Niño, the trade winds weaken and the central and eastern tropical Pacific runs warmer than average. During La Niña, the trade winds strengthen and the same waters run cooler. Both shift weather patterns worldwide.
Polar Vortex: Guides and Explainers
These explainers connect this definition to real-world forecasting and decision-making.
In-depth guide
What Is the Polar Vortex? Understanding Extreme Winter Cold
Learn what the polar vortex is, how it affects winter weather across North America, why it sometimes 'breaks down' to deliver extreme cold, and what to expect during polar vortex events.
Weather Education
What Is an Atmospheric River? The AR Scale, the Pineapple Express, and El Niño
Learn what an atmospheric river is, how the AR 1 to 5 scale works, what a Pineapple Express is, and whether a very strong El Niño means more of them for the West Coast this winter.
Weather Education
El Niño 2026: How Strong It Is, and What It Actually Means
El Niño is strengthening in 2026, with NOAA calling a strong-to-very-strong event likely through winter and 83% odds of a historic peak that exceeds every event since 1950. What that means for hurricane season and winter.
Helpful Tools and Hubs
Use these pages to apply the concept, compare conditions, or follow related weather workflows.
Tool
Wind Chill Calculator
Estimate cold-weather exposure risk from temperature and wind speed.
Seasonal Hub
Winter Weather Guide
Find practical explainers on snow, freezing rain, wind chill, and winter travel risk.
Guide
High Pressure vs Low Pressure
How high and low pressure systems work, and why they determine whether you get sunshine or storms.
Guide
Barometric Pressure Explained
What barometric pressure means, how it predicts weather changes, and how to read pressure trends.
Sources
Explore Other Terms
Pineapple Express
A strong atmospheric river that carries moisture from the tropical Pacific near Hawaii to the West Coast of North America. Because the air is warm, a Pineapple Express raises mountain snow levels, so more precipitation falls as rain and can melt existing snowpack, increasing the flood risk.
Barometric Pressure
The weight of the atmosphere pressing down on a given point, measured in inches of mercury (inHg) or millibars (mb). Rising pressure typically indicates improving weather, while falling pressure suggests approaching storms or precipitation.
Velocity
Doppler radar measurement of how fast precipitation is moving toward or away from the radar. Velocity data reveals wind patterns, rotation in thunderstorms, and potential tornado signatures that reflectivity alone cannot show.
ECMWF
ECMWF is the European Centre for Medium-Range Weather Forecasts, an intergovernmental organization supported by 35 states, and the name commonly given to its global weather model, often called the European model or the Euro. Its physics-based Integrated Forecasting System (IFS) runs on a global grid of about 9 km and forecasts up to 15 days ahead.
VFR
Visual Flight Rules allow flight using visual references when the applicable visibility and cloud-clearance minimums are met. Those minimums vary by airspace class, altitude, and day or night under 14 CFR 91.155. Separately, the VFR weather category means a ceiling above 3,000 feet and visibility greater than 5 statute miles.
Storm Surge
Storm surge is an abnormal rise in sea level during a hurricane or other intense storm, measured as the height of the water above the normal predicted tide. It is produced mainly by the storm's winds pushing water toward the shore. Storm surge is the leading cause of deaths from hurricanes.
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