In 2017, a total of 16 disasters cost $1 billion or more, and led to at least 362 deaths, said the report by the National Oceanic and Atmospheric Administration.
The death toll could be substantially higher, once Puerto Rico completes its review of deaths from Hurricane Maria, experts said.
The year far outpaced the previous record, set in 2005 with losses of $215 billion largely due to Hurricanes Katrina, Wilma and Rita.
With a total price tag of $265 billion, 2017 was the most expensive hurricane season on record, the report said.
Hurricane Harvey, which dumped some 50 inches (127 centimeters) of rain on Texas, cost $125 billion, second only to 2005's Hurricane Katrina in historical records of billion-dollar disasters, going back to 1980.
Hurricane Maria, which flattened much of Puerto Rico, cost $90 billion, while Hurricane Irma, which plowed into the Caribbean and Florida, cost $50 billion.
"Hurricane Maria now ranks as the third costliest weather and climate disaster on record for the nation and Irma ranks as the fifth costliest," said the report.
Last year's western wildfire season -- which ravaged large parts of California -- cost $18 billion, "tripling the previous US annual wildfire cost record," said the report.
NOAA said the number of billion-dollar disasters -- 16 -- tied with 2011 for the most in a single year.
They included two flooding events, one freeze event, eight severe storm events, three tropical cyclones, one drought and one wildfire.
In historical context, these expensive storms are becoming far more common.
The annual average of billion-dollar storms from 1980 to 2017 is 5.8, said NOAA.
But in the last five years, among the warmest on record, the average has reached 11.6.
The costs include estimates of both insured and uninsured losses, but are likely below the true costs because they do not include health care costs.
Heat records
Last year was also the third warmest on record in the United States, following 2012 and 2016, NOAA said.
The year's average temperature was 54.6 Fahrenheit (12.2 C), 2.6 F (1.4 C) above the 20th century average.
"The five warmest years on record for the contiguous US have all occurred since 2006," said the report.
Every US state on the mainland and Alaska had above-average temperatures for the third year in a row.
Five states had their hottest year on record: Arizona, Georgia, North Carolina, South Carolina and New Mexico.
A warming climate can exacerbate the frequency and severity of certain kinds of storms, including hurricanes, fires and floods, experts say.
"The long-term signal is tied with long-term warming," said Deke Arndt, chief of the monitoring section at NOAA's National Centers for Environmental Information.
However, that warming trend does not erase the likelihood of fierce winter storms.
"We do live in a warming world but we still have very cold colds," he told reporters on a conference call.
"We are still going to see blue blobs on the map."
Despite cold snaps in various parts of the nation throughout the year, above-average temperatures in other parts of the year more "than offset any seasonal cool conditions," said the report.
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