White Christmases may be a diminishing dream

OAK RIDGE, Tennessee (CNN) -- Chances of a white Christmas in many parts of the United States are slimmer at the start of the 21st century than they were 40 years ago, according to a survey by the Oak Ridge National Laboratory in Tennessee.

Comparing data for 16 cities across the United States, scientists found a drop in the number of cities that recorded at least 1 inch of snow on the ground December 25.

In the 1960s, the cities had a total of 78 white Christmases, an average of almost five per city. By the 1990s, the total for the decade was down to 39, for an average of about 2.4 per city.

The survey found differences between various areas of the country. For the big cities of the Northeast and Midwest, the decline in white Christmases is more pronounced.

Combining data for New York; Boston, Massachusetts; Washington; Chicago, Illinois; Detroit, Michigan; and Cincinnati, Ohio, the number drops from 36 white Christmases in the 1960s to 10 in the 1990s.

Farther west, the numbers have stayed fairly constant.

In Denver, Colorado; Salt Lake City, Utah; and Tahoe City, California, the study found 19 white Christmases in the 1960s, 18 in the 1970s, 23 in the 1980s and 19 in the 1990s.

The study also included some Southern cities.

For three cities in Tennessee, the total number of white Christmases went from nine in the 1960s to none in the 1980s and 1990s. Atlanta, Georgia, hasn't had an official white Christmas since record-keeping began in 1896.

Oak Ridge researchers caution against reading too much into the survey. They said it looks at one aspect of weather on one particular day of the year and doesn't prove anything as far as a long-term climate change.