Average temperatures between December and February have warmed markedly over the past 150 years. Trend toward warmer temperatures has diminished snow prospects in an area that often rides the rain-snow line. Number of days with snow cover has dipped from an average around 20 in 1900 to just 10 today. D.C.’s snow season is getting shorter, tied to rising temperatures in December and March. In recent years, unseasonably mild air is being drawn northward more frequently, especially in February. Five of Washington’s 10 largest snowstorms since 1996 have occurred since 1996.
