LAST year was the warmest on record for the US and was also the second most extreme weather year yet recorded.

The hot weather contributed to a record drought which, at its peak, parched 61 per cent of the nation, the National Oceanic and Atmospheric Administration said.

Those dry conditions helped spark massive wildfires which charred 9.2 million acres - the third highest on record.

The nation suffered through 11 weather disasters that caused $US1 billion ($A956.89 million) in damage, including hurricanes Sandy and Isaac and tornado outbreaks in the Great Plains, Texas and Ohio Valley.

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 nationally-averaged precipitation total of 67.5 centimetres was 6.5 centimetres below average and the 15th driest year on record.

This was also the driest year for the nation since 1988, when 64.1 centimetres of precipitation were observed.

Meanwhile, 2012 was the third year in a row with 19 named tropical storms, 10 of which packed hurricane strength. One was a major hurricane.