The meteorologists over at The Weather Chanel define a “White Christmas” as “One in which there is at least one inch of snow on the ground on Christmas morning. It doesn’t have to be snowing on the holiday for that to happen, of course.”
A large swath of the country can thank persistently cold weather for maintaining their snow coverage and improving chances for a White Christmas:
“A persistently cold pattern through the Christmas holiday should keep any snow from melting over a large part of the northern tier of states from parts of the Northwest, through the northern and central Plains, Upper Mississippi Valley, Great Lakes, and Northeast.”
This map shows where there is the best chance for a White Christmas in any given year, based on climatological averages over the last three full decades:
