A polar vortex will affect large regions of North America beginning Wednesday and lasting through the weekend as 2016 begins to wrap up.
A polar vortex occurs when frigid air from the North Pole and the arctic region around it dips southward and sometimes causes unusually cold temperatures in parts of North America, according to NBC News. A polar vortex usually happens when the air mass weakens in winter, and cold air follows the jet stream south.
The polar vortex is only in the stratosphere, NBC News meteorologist Sherry Pugh said, so it doesn’t cause snow and ice directly, although any precipitation is likely to be frozen because of temperatures being so low. The polar vortex is always there around the poles.
“It doesn’t come and go,” Pugh said. “It does weaken and strengthen, and that’s how it fuels the weather around the world.”
The current polar vortex is slated to bring unusually cold temperatures to the Northern Plains and Upper Midwest midweek and reach the East Coast and Southeast by week’s end, according to USA Today. WeatherBell Analytics meteorologist Ryan Maue said it will be similar to the January 2014 polar vortex, but will not bring record-breaking cold.
High temperatures may only be in the single digits for the Upper Midwest on Wednesday and Thursday, the Weather Channel said, and windy conditions could make those temperatures feel like they are below zero in many parts of the country from Chicago to Pennsylvania and the Northeast.
The polar vortex is not affected by climate change, NBC News reported, so the cold temperatures will not moderate even if the climate is getting warmer.