Today we are having a temporary reprieve from the extreme cold we have had for most of January. More extreme temperatures are expected by next Monday, however.
The postcard above has a wind chill factor chart showing how cold the temperature feels at various combinations of actual temperature and wind speed. The National Weather Service has more information about wind chill along with a downloadable chart and brochure here.
The next postcard probably needs some explanation for those not familiar with cold weather. It is kind of a joke that a tongue will freeze and stick to a metal post when the temperature is below zero, but it can actually happen. At "forty below it just doesn't matter" whether the temperature scale is Fahrenheit or Celsius because at that point both are the same number. For conversions between Fahrenheit and Celsius at other points, see the chart here.