It’s stopped trains and planes, driven up energy use and may deliver the coldest day across the United States in almost 20 years. The ferociously cold air mass has sent a chill through about half of the country’s population. New York Governor Andrew Cuomo declared a state of emergency in 14 counties, saying a “truly extraordinary” weather event was expected. The freezing weather also poses a threat to crops and is expected to reach as far south as Texas and Florida, according to weather observatories. The extreme weather has been blamed for more than a dozen deaths.