The Northern Plains and Great Lakes are set to endure a week of intensely cold conditions, with daytime highs struggling to rise above the teens and twenties. An influx of Arctic air, driven southward by a series of clipper systems, will exacerbate the cold, severely restricting daytime warming and creating dangerously low wind chills. Expect variable skies, alternating between cloudy and partly clear, as minor disturbances pass through the region.