According to the National Oceanic and Atmospheric Administration (NOAA), a "white Christmas" is defined as having one inch or more of snow on the ground Christmas morning. Statistical data was compiled from the averages of several climatological measurements between 1981 and 2010, including daily and monthly normal temperature, precipitation, snowfall, heating and cooling degree days, frost/freeze dates and growing degree days. While the map shows the climatological probability of snow-covered ground on December 25, the actual conditions on any given year may vary widely. It is also important to note that just because a certain location may have at least 1 inch of snow on the ground doesn't mean it is fresh snow. That 1 inch could have come down two days prior, but very cold temperatures kept the snow in place for Christmas Day.

Source: CNN December 19, 2020 13:41 UTC