The eastern United States is bracing for a significant cold snap as a polar vortex descends, bringing with it arctic temperatures throughout January. Meteorologists predict that a deep southward dip in the jet stream will funnel frigid air masses into the central and eastern regions of the country, affecting states from Minnesota and the Dakotas all the way to New England and northern Florida. Cities such as Chicago and New York are expected to experience temperature fluctuations, with periods dropping 10 to 20 degrees below the average for late January.