USA Today Thu Dec 6, 2012 12:02 PM

Unseasonable warmth across the country this week likely has sealed the deal: 2012 will go down as the warmest year in U.S. history, according to data released Thursday by the National Climatic Data Center in Asheville, N.C.

“We are very certain of this,” reports climate center scientist Jake Crouch.

So far this year, the United States has had a national average temperature of 57.1 degrees, 3.3 degrees above average and a full degree above the previous warmest year, which was 1934.

U.S. weather records date to 1895.

A total of 18 states in the central and northeastern United States have had record warmth this year and an additional 24 states are seeing a Top 10 warm year. No states are seeing a cooler-than-average year.

The heat also has kept much of the nation drier than average this year, helping contribute to the USA’s worst drought since the 1950s and the second-worst wildfire season on record in acreage burned.

So far, three states -- Wyoming, Colorado and Nebraska -- are seeing their driest year on record.

For 2012 not to be the warmest year on record, December would have to be 1 degree colder than any other December, and so far it’s been unusually warm, 5-10 degrees above average.

Snow is covering only 7 percent of the United States now, the lowest percentage for this date since 2003.