The polar vortex, as explained by the National Weather Service, is a large area of low pressure and cold air that encircles the Earth’s poles. Even though it’s often framed in the media as a weather anomaly, the polar vortex is a constant feature of the atmosphere that simply weakens in the summer and strengthens in the winter.

The polar vortex is not synonymous with cold snaps, but when it slides toward the United States, the polar jet stream can mirror the distortion and introduce Arctic air. While this distortion is often caused by weakening of the polar vortex, that’s not the case this time.