WASHINGTON — America smashed the record for billion-dollar weather disasters this year with a deadly dozen – and counting.

With an almost biblical onslaught of twisters, floods, snow, drought, heat and wildfire, the U.S. in 2011 has seen more weather catastrophes that caused at least $1 billion in damage than it did in all of the 1980s, even after the dollar figures from back then are adjusted for inflation.

The National Oceanic and Atmospheric Administration added two disasters to the list Wednesday, bringing the total to 12. The two are the Texas, New Mexico and Arizona wildfires and the mid-June tornadoes and severe weather.

NOAA uses $1 billion as a benchmark for the worst weather disasters.

Extreme weather in America this year has killed more than 1,000 people, according to National Weather Service Director Jack Hayes. The dozen billion-dollar disasters alone add up to $52 billion.

The old record for $1 billion disasters was nine, in 2008.

Hayes, a meteorologist since 1970, said he has never seen a year for extreme weather like this, calling it “the deadly, destructive and relentless 2011.”

Officials are still adding up the damage from Tropical Storm Lee and the pre-Halloween Northeast snowstorm – so far each is at $750 million. And 2011 isn’t over.

Scientists blame an unlucky combination of global warming and freak chance. They say even with the long-predicted increase in weather extremes triggered by man-made climate change, 2011 in the U.S. was wilder than predicted. The six large twister outbreaks can’t be attributed to global warming, scientists say.

“It would be tempting to say it’s a sign of things to come, though we would be hard-pressed to see such a convergence of circumstances occurring in one single year again for a while,” said Jerry Meehl, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo.

Another factor in the rising number of billion-dollar calamities: “More people and more stuff in harm’s way,” such as in coastal areas, said NOAA Administrator Jane Lubchenco.

“What we’re seeing this year is not just an anomalous year, but a harbinger of things to come,” with heat waves, droughts and other extremes, Lubchenco said Wednesday at an American Geophysical Union science conference in San Francisco.

The number of weather catastrophes that pass the billion-dollar mark when adjusted into constant dollars is increasing. In the 1980s, the country averaged slightly more than one a year. In the 1990s, it was 3.8 a year. It jumped to 4.6 in the first decade of this century. And in the past two years, it has averaged 7.5.

Other years had higher overall damage figures because of one gargantuan disaster, such as Hurricane Katrina in 2005.

The world has to do two things, said Princeton University geological sciences professor Michael Oppenheimer: Try to slow global warming by reducing greenhouse gas emissions and prepare better for extreme weather.