WASHINGTON (AP) — Anchorage, Alaska, was warmer Tuesday than Jacksonville, Florida. And it snowed Wednesday in Tallahassee, Florida, for the first time in 28 years.

The weather in the U.S. is that upside down.

That’s because the Arctic’s deeply frigid weather escaped from the atmospheric jail that traps the worst cold. It then meandered south to the central and eastern United States.

And this has been happening more often in recent times, scientists say.

WHY IS IT SO COLD?

Super cold air is normally locked up in the Arctic in the polar vortex, which is a gigantic circular weather pattern around the North Pole. A strong polar vortex keeps that cold air hemmed in.

“Then when it weakens, it causes like a dam to burst,” and the cold air heads south, said Judah Cohen, a winter storm expert for Atmospheric Environmental Research, a commercial firm outside Boston.

“This is not record-breaking for Canada or Alaska or northern Siberia — it’s just misplaced,” said Cohen, who had forecast a colder than normal winter for much of the U.S.

IS THIS UNUSUAL?

Yes, but more for how long — about 10 days — the cold has lasted, than how cold it has been. More than 1,600 daily records for cold were tied or broken in the last week of December, according to the National Oceanic and Atmospheric Administration. Far fewer all-time records were set. In other words, the minus 20 degrees in Omaha on Jan. 1 was the coldest New Year’s Day since record-keeping began in 1871. But that didn’t come near Omaha’s all-time record low of minus 32, set Jan. 5, 1885, according to the National Weather Service.

For Greg Carbin of the weather service’s Weather Prediction Center, the most meaningful statistic is the average temperature during the cold streak. In Nebraska, for example, Hastings, Lincoln and Grand Island had their coldest final week of December since record-keeping began in the late 1800s. Omaha, with only one daily temperature record that week, still managed to notch its third-coldest final week of the year. And remember, Omaha’s records go back to 1871.

IS IT JUST THE U.S.?

Pretty much. While the continental United States has been in the deep freeze, the rest of the globe has been toastier than normal. The globe as a whole was 0.9 degrees warmer than normal Tuesday and the Arctic was more than 6 degrees warmer than normal, according to the University of Maine Climate Change Institute.

WHAT’S THE LATEST?

Tallahassee got its first measurable snow in nearly three decades on Wednesday. The snow brought a childlike joy and wonder and loud whoops from longtime residents who rarely see the white stuff.

Much of the Southeast’s Atlantic Coast got a wintry mix of snow and freezing rain as the storm headed north.

The number of deaths linked to the relentless cold across much of the United States has risen to 17. The latest were in Texas, Mississippi and Michigan.

WHAT'S NEXT?

The weather service says an intense storm embedded in the system is expected to intensify so rapidly that it will qualify as a “bomb cyclone.” That’s one where the pressure at the center of a storm drops very rapidly.

The storm should dump at least 8 inches of snow today on Boston — where some flights are already canceled — and at least six inches on New York City.

Still, meteorologists say most of the storm’s fierce hurricane-force winds should stay out to sea until it nears Canada. Meteorologists say that perhaps the worst effects could be bitter subzero cold on the East Coast.

“For the Northeast, this weekend might be the coldest of the coldest with the storm,” said Jason Furtado, a University of Oklahoma meteorology professor. “We could be ending (the cold snap) with a big hurrah.”

WHAT MAKES THE POLAR VORTEX MOVE?

This is an area of hot debate and research among scientists and probably is a mix of human-caused climate change and natural variability, Furtado said. Climate change hasn’t made the polar vortex more extreme, but research indicates that global warming is allowing arctic air to make more prolonged, deep dives into the U.S.

That vein of research also indicates a possible connection between stalled weather systems at other times of the year. Global warming could be responsible for “stuck” spring and summertime weather patterns in which flooding rains or searing drought takes hold.

HOW CAN IT BE SO COLD WITH GLOBAL WARMING?

Arctic air is still bitterly cold, so atmospheric changes that allow that air to drop south will continue to lead to such sharp temperature drops. And don’t confuse weather — which occurs over a few days or weeks at a regional level — with climate, which spans over years and defines the region’s habitability. Weather is like a person’s mood, which changes frequently, while climate is like someone’s personality, which is more long-term, Furtado said.

“A few cold days doesn’t disprove climate change. That’s just silly. Just like a couple of down days on the stock market doesn’t mean the economy is going into the trash.”

World-Herald staff writer Nancy Gaarder contributed to this report, which also includes material from the Washington Post.

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