Steam Fog
Steam fog, also called sea smoke (or in this case, river smoke) or frost smoke, is formed when very cold air mixes with a shallow layer of saturated warmer air over a body of water. As the warmer air is cooled beyond the dew point, it can no longer hold as much water vapour, and the excess condenses out, producing a steam or smoke effect. On a recent very cold January day, I snapped this photograph of a smoking St. Lawrence River.
Willow House Chronicles 