ICE FOG

A type of cloud near ground which is made of tiny particles of ice instead of water droplets. The dew-point temperature in this case must be well below freezing (less than -40° C) or else supercooled liquid droplets are likely to form instead. Like fog, it forms in clear and calm weather conditions. Ice fog is most common at high latitudes where those extremely cold temperatures and dew-point temperatures are most common.