Ice-breakers on Lake Michigan as US weather worsens
6 January 2014 Last updated at 16:14 GMT
Parts of the US are braced for potentially record-breaking low temperatures as a "polar vortex" brings more freezing weather.
Temperatures in the north and central US could feel as low as -51C (-60F) with the effect of wind chill, forecasters say.
ABC News reports that ice-breakers have been deployed to Lake Michigan to clear the way for freighters.