Summary:

• **The Polar Vortex and Jet Stream**: A weather pattern called the polar vortex sometimes wobbles and moves south, bringing extremely cold air to the eastern United States. When this happens, the jet stream (a river of fast-moving air high in the atmosphere) gets pushed around, which can make the western part of the country warmer than usual at the same time.

• **Why This Happens**: Scientists believe that changes in sea ice in the Arctic and warming ocean temperatures can affect how the polar vortex behaves. When there's less ice in the Arctic, it can change wind patterns and push cold air toward the east while warm air moves into the west, creating very different weather on opposite sides of the country.