A polar vortex broke, and severe temperatures are set to dominate most of the United States, including the Midwest, in the coming days.

A forecast model is essentially a supercomputer that attempts to simulate behaviors in the atmosphere. An ensemble refers to a group of these supercomputers, each of which has a different variation. This allows us to assign a probability to a certain weather event happening.

According to the National Weather Service, prolonged exposure to extreme cold can quickly lead to frostbite or hypothermia. Frostbite most often affects uncovered skin and extremities, like fingers, toes and ears. Hypothermia develops when the body loses heat more rapidly than it can produce it.

Forecasters have said parts of the U.S. can expect frigid temperatures in December. A first round has arrived, and more cold air could be coming.

Will the sun be shining on your Thanksgiving meal this year? It’s not likely, according to projections. And that’s not just because the sun will set in the Harrisburg area around 4:43 p.m. on Nov. 27.