If you plan to go over the river or through the woods this Thanksgiving, consider snow tires. The holiday falls on Nov. 28 this year, and for the northern parts of the northeast United States, that means a good chance of snow.

Cornell University's Northeast Regional Climate Center predicts a 67 percent likelihood of an inch of snow on the ground in Caribou, Maine, on Thanksgiving morning, and a 34 percent possibility in Burlington, Vt. Not far behind is Concord, N.H., with a 29 percent chance. Keith Eggleston, senior climatologist at the center, based his predictions on a 30-year average of Northeast snowfall, from 1971 to 2000.

"Even though Thanksgiving this year is late in November, the chances are we won't see snow in places like New York City, Baltimore and Philadelphia," said Eggleston. Each of those cities has a zero percent chance of snow on Nov. 28, which means that snow has not fallen on that date in the past three decades. Three New York cities, Buffalo, Albany and Ithaca, have a 24 percent likelihood of snow, while Wilkes-Barre, Pa., has a 12 percent chance.

Thanksgiving this year falls on the latest date allowed by U.S. law (the fourth Thursday in November). The day became a national holiday during the Civil War following a suggestion to the White House by children's author Sarah Josepha Hale. In 1863 President Lincoln proclaimed that Thanksgiving would fall on the last Thursday in November, a national tradition maintained until 1939.

But in 1939 retailers realized that Thanksgiving would fall on Nov. 30, making for a short holiday-shopping season. They asked President Roosevelt to change the day to Nov. 23, which he did by proclamation. Many Americans opposed the change and celebrated the holiday on Nov. 30 anyway, according to Ann Marie Gleeson of the Roosevelt Presidential Library and Museum in Hyde Park, N.Y.

In 1940 Roosevelt issued a proclamation moving Thanksgiving to Nov. 21 from Nov. 28. But after studies by the U.S. Department of Commerce showed that moving Thanksgiving back a week would not affect retail sales, on Dec. 26, 1941, Roosevelt approved a joint resolution of Congress that decided -- once and for all -- that Thanksgiving would fall on the fourth Thursday of November.

Related World Wide Web sites: The following site provides additional information on this news release.

o FDR Library: "The Year We Had Two Thanksgivings":

http://www.fdrlibrary.marist.edu/thanksg.html

Probability of a White Thanksgiving (Nov. 28)
Data compiled by the Northeast Regional Climate Center at Cornell University.