Photograph by Frank Franklin II, AP
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People pose for photographs in front of a frozen water fountain at Bryant Park, Thursday, Dec. 28, 2017, in New York. A large swath of northern New York is encased in ice and snow after days of lake-effect storms followed by an arctic cold front sending temperatures well below zero.

Photograph by Frank Franklin II, AP

What Makes This New Year's Eve Cold Snap So Unusual

Freezing conditions are blanketing parts of the U.S., but other spots are warmer than usual.

It's cold. Really cold. And for much of the eastern United States, there's no relief in sight.

Some New Jersey towns have cancelled their annual polar plunges. In Massachusetts, two dead sharks washed up on beaches after experiencing "cold shock," and low temperatures continue to grip the area. (Related: "Why Is Record Cold and Epic Snow Hitting the U.S. So Early?")

President Donald Trump tweeted from Florida Thursday that maybe the East Coast would benefit from some climate change:

But why is it so cold? Perhaps more importantly, how long is it going to be so cold?

Cold Weather, Warm Climate

Climate and weather are not the same thing. Climate represents the overall course of weather conditions over time, while weather changes day to day. One meteorological expert put it well: "weather is your mood and climate is your personality."

Weather Versus Climate Change Neil deGrasse Tyson breaks down the differences between weather and climate change.

It's not unusual for winters in the U.S. to be frosty; late December through January are the nation's coldest weeks. It is strange, however, that these spells are lasting as long as they are, says Minnesota-based meteorologist Eric Holthaus.

Under normal conditions, a cold spell might go on for three or four days. Right now, some spots in the country are seeing ten-day stretches of cold.

"The longevity of it is a bit unusual," Holthaus says from Saint Paul, where temperatures have been hovering around zero degrees Fahrenheit. "It's just a really localized thing that's happening right now."

Warm Elsewhere

But other parts of the country are warmer than normal. Alaska's December was the warmest it’s seen in years, and California's unrelenting dry season doomed the state to a series of devastating wildfires in the last few months. (Read "These 4 Things Need to Happen to End California's Drought.")

"We're having record lows and record highs at the same time," Holthaus says.

In July, researchers published a study saying warmer Arctic conditions lead to colder temperatures in parts of North America. At the time, Carnegie Institution for Science researcher Anna Michalak warned that Arctic melting has immediate impacts on weather conditions in lower latitudes. (See "Extreme Research Shows How Arctic Ice Is Dwindling.")

"Winters could be harsher," Michalak told National Geographic in July. "By emitting greenhouse gasses, we're not just warming temperatures, we're perturbing the Earth's entire system."

Weather models can only predict temperatures into the next week or two, and the models are still showing cold waves across some parts of the U.S. Holthaus estimates the cold spells could last about a week to ten days, but it's too soon to say if this long stretch of cold is being caused by climate change. (Take this quiz to see how much you know about winter weather.)

Why It’s Hard to Forecast the Weather

"It's really difficult to say for certain if this exact weather pattern today would have happened the same way without climate change," Holthaus says. "It's really irresponsible to say that climate change is not affecting weather everywhere on Earth."

If you're going out any time soon, NOAA recommends bundling up to protect yourself from frostbite and hypothermia.