Last year was the second hottest on record in mainland United States, and included 10 major weather and climate events that each led to more than US$1 billion (NZ$1.48 billion) in damages.
According to the National Oceanic and Atmospheric Administration, the average temperature in 2015 was 12.4C, compared with 12.9C in 2012, the warmest year recorded since the government started keeping records in 1895.
Much warmer than average annual temperatures were recorded across the west, including Washington state and Oregon, as well as in the southeast, including Florida.
It was also the third wettest year on record, with Oklahoma and Texas setting records for precipitation.
The extreme climate and weather events in 2015 included storms, floods and a wildfire that each caused more than US$1 billion in damages, NOAA said. These events resulted in the deaths of 155 people.
Last November, the World Meteorological Organization said that 2015 would be the hottest on record globally, and 2016 could be even hotter due to the El Niño weather pattern.
At the United Nations' climate summit in Paris last month, nearly 200 countries agreed to take steps to fight climate change, but whether their actions will achieve a goal of restraining a rise in temperatures to "well below" 2C above pre-industrial levels is uncertain.
Though 2015 was the 19th straight year that the annual average temperature exceeded the 20th century average, according to NOAA, climate change has received scant attention on the presidential campaign trail among the Republican candidates.
Ahead of the November election, Republican candidates have criticised President Barack Obama and leading Democratic candidate Hillary Clinton for posing climate change as a top national security issue, saying the assertion understates the threat of terrorism.