A significant cold air mass is sweeping across the central and southern United States, bringing with it unseasonably chilly temperatures and the threat of frost. Following the passage of a strong weather front, a surge of frigid air will cause temperatures to plummet well below the average for this time of year across a large swath of the country. Daytime highs are expected to range from the 50s to 60s Fahrenheit, providing a stark contrast to the warmer conditions experienced recently.