epa10446996 Sea smoke, forms over the water of Boston Harbor, in Boston, Massachusetts, USA, 04 February 2023. Sea smoke, or steam fog, forms when cold air flows immediately over warmer water. A cold airmass moved into the region setting a new record low temperature for Boston of -9 F (-22.7C), along with wind gusts of 35 mph to 50 mph (56.33kph to 80.47kph) driving windchill temperatures to as low as -40F (-40C). EPA/CJ GUNTHER