(NBC News) -- If you found yourself bundling up in scarves, hats, and long underwear less than usual last year, you weren't alone: 2012 was the warmest year on record in the contiguous United States, according to scientists with The National Oceanic and Atmospheric Administration.
"We're taking quite a large step," said Jake Crouch, a climate scientist from the NOAA National Climatic Data Center, which has recorded temperatures in the contiguous U.S. for the past 118 years.
It was also a historic year for "extreme" weather, scientists with the federal agency said. With 11 disasters that surpassed $1 billion in losses, including Superstorm Sandy, Hurricane Isaac, and tornadoes across the Great Plains, Texas, and the Southeast and Ohio Valley, NOAA said 2012 was second only to 1998 in the agency's "extreme" weather index.
A long-term warming trend for the U.S., combined with drought and a northerly jet stream, led to the record heat, explained Crouch.
"During the winter season, the jet stream tended to stay further north of the U.S.-Canadian border, so that limited colder outbreaks in the country. It also limited precipitation. So that led to a warm and dry winter season, and that persisted through the spring," he said.
"That warm and dry spring and winter laid the groundwork for the drought we had this summer... . When we have drought, it tends to drive daytime temperatures upward."
The unprecedented warm weather wasn't contained to the United States.
A corresponding rise in global temperatures prompted the World Meteorological Organization to call the rate at which the Arctic sea ice was melting "alarming" in its Nov. 28, 2012, report.
"The extent of Arctic sea ice reached a new record low. The alarming rate of its melt this year highlighted the far-reaching changes taking place on Earth's oceans and biosphere. Climate change is taking place before our eyes and will continue to do so as a result of the concentrations of greenhouse gases in the atmosphere, which have risen constantly and again reached new records," World Meteorological Organization Secretary-General Michel Jarraud said.
Each year since 2001 has been among the warmest on record worldwide, with 2012 likely to "be no exception despite the cooling influence of La Niña early in the year," the report added.
NOAA expects to have global data for 2012 sometime in the coming weeks, but Crouch said scientists already know with certainty "it's going to be in the top ten" warmest years ever.
Adding to the extremes: 2012 was the driest year on record for the U.S., with 26.57 inches of average precipitation -- 2.57 inches below average. Those dry conditions created an ideal environment for wildfires in the West, which charred 9.2 million acres -- the third highest amount ever recorded, NOAA said Tuesday.
Other notable climate activity from 2012:
While NOAA made no meteorological forecasts for 2013, Crouch said the drought was going to continue to be an issue.
"The drought got a lot of attention this summer when it was having impacts on agriculture. More than 60 percent of the country is still in drought," he said. "And if things don't change, the drought is going to continue to be a big story in 2013."