The United States says last year was the warmest ever in the country.

Government weather experts said Tuesday the average 2012 temperature in the country's 48 contiguous states — not counting the island state of Hawaii and far northern Alaska — was 55.32 degrees Fahrenheit . That was a full degree higher than the old record set in 1998. It also was more than three degrees higher than the average for the entire 20th century.

As the Earth's climate changes, the U.S. has experienced a long-term warming trend. The National Oceanic and Atmospheric Administration said a summertime drought that covered vast reaches of the country's agricultural heartland and a northerly jet stream contributed to last year's record warmth.

In addition, the government said it was the second worst year on record in the U.S. for extreme weather, with 11 natural disasters each causing more than $1 billion in damage. Among the worst were Superstorm Sandy that hit the country's heavily populated northeastern seaboard in late October, Hurricane Isaac that struck the southern coastline and numerous tornadoes.

Weather data for 2012 from throughout the world is expected next week. Through 11 months, the Earth was on pace to have its eighth warmest year on record.