Last year was the hottest on record in the US, according to the government agency which monitors weather events.
The National Oceanic and Atmospheric Administration ( NOAA ) also said 2012 saw the second-most extreme weather ever.
The 2012 average national temperature was pushed up to 13C (55.32F) thanks to widespread drought and a mostly absent winter.
That broke the previous record, set in 1998, by an unprecedented 0.6 Celsius or full degree Fahrenheit.
Last year’s hot weather contributed to a record drought which, at its peak, parched 61% of the nation, destroyed crops worth billions of dollars and slowed shipping on the Mississippi River as water levels reached historic lows.
The dry conditions helped spark massive wildfires that charred 9.2 million acres, the third highest annual figure on record.
The nation suffered 11 weather disasters that each caused \$1bn (£620m) in damage or more, including hurricanes Sandy and Isaac and deadly tornado outbreaks in the Great Plains, Texas and the Ohio Valley.
Scientists have warned that such conditions are just a taste of what is to come as a result of climate change, prompting advocates to urge swift action to limit the impacts.
Hurricane Sandy proved the most destructive disaster of 2012 after it made landfall near New York, killing 131 people, knocking out power to eight million people and destroying tens of thousands of homes and businesses.
Last year was the third year in a row with 19 named tropical storms, 10 of which packed hurricane strength. One was a major hurricane.
Some relief came from one of the slowest tornado seasons in decades, with just 878 confirmed twisters and 58 reports still pending review.
However, it was still a deadly and destructive year. Three tornado outbreaks caused extensive damage and there were 68 tornado-related fatalities.
Every one of the 48 states in the continental US had an above-average annual temperature in 2012 and 19 of those broke records.
The warm temperatures meant that the winter season "was nearly non-existent for much of the eastern half of the nation", the NOAA said.
July also broke records with an average temperature of 24.9C (76.9F), the hottest month ever observed for the contiguous United States.
A sweltering June and August contributed to making 2012 the second hottest summer on record, with almost 100 million people - nearly a third of the nation - sweating through 10 or more days of summer temperatures greater than 37C (100F).
The nationally-averaged precipitation total of 67.5cm (26.57in) was 6.5cm (2.57in) below average and the 15th driest year since record-keeping began in 1895.
The US Climate Extremes Index - which evaluates extremes in temperature and precipitation along with tropical storms that make landfall - was nearly twice the average value and second only to 1998.