Freezing rain air at the surface within the region of high pressure. The warm air from the Gulf of Mexico is often the fuel for freezing precipitation. Freezing rain develops when falling snow encounters a layer of warm air aloft, typically around the 800 mbar (800 hPa) level, causing the snow to melt and become rain. As the rain continues to fall, it passes through a layer of subfreezing air just above the surface and cools to a temperature below freezing (). If this layer of subfreezing air is sufficiently deep, the raindrops may have time to freeze into ice pellets (sleet)
The Great Snow of 1717 February 27 or March 1. On February 27 a typical New England nor'easter passed through, with snow falling on some areas and other places receiving a mix of snow, sleet, and rain. The first major snowstorm occurred on March 1, with another on the 4th, and a third, the worst among the three, on the 7th. At some points, the snow would lighten and stop, but the sky would remain cloudy, showing no signs of clearing. Some of the oldest Native Americans had said that even their ancestors never spoke of a storm of this magnitude. Boston received around of