Wacky weather

Time-lapse shows shocking temperature changes between December and January

It’s not just your imagination.

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This winter’s weather has been quite unpredictable.

In late December, extreme cold struck much of the U.S. and Canada.

Northeastern cities were buried in snow while dangerous whiteout conditions swept the Midwest.

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Just a few weeks later, it warmed up so much that some areas saw record-breaking warmth for this time of year.

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On January 4, at least seven U.S. cities saw their highest temperatures ever recorded for that day, according to the Washington Post.

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The rapid temperature change seemed to happen at breakneck speed.

To visualize the drastic shift, NASA’s Earth Observatory mapped out daily surface air temperatures from December to early January.

This is the surface air temperature of North America from Dec. 1 to Jan. 2. Pulses indicate slight changes between day and night temperatures.

Joshua Stevens/NASA Earth Observatory

Notice when the artic blast balloons across the continent on Dec. 23, bringing temperatures down across the U.S.

Joshua Stevens/NASA Earth Observatory

On the left are surface air temperatures on Dec. 23. Look at the drastic warming that unfolded just six days later on Dec. 30.

Joshua Stevens/NASA Earth Observatory

So what caused this wacky weather?

You can thank the polar vortexa powerful ball of swirling, cold winds in the stratosphere that forms above the North Pole every winter.

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Sometimes the polar vortex will weaken and stretch for short periods of time — about a week or so.

When that happens, the polar jet stream in the troposphere (below the polar vortex) often stretches with it, carrying cold winds to regions below the Arctic.

That’s likely what happened in December; the polar vortex stretched, causing the polar jet stream to carry chilly air to North America.

NOAA

When the polar vortex rebounded, temperatures in the U.S. increased due to warm air from the equator moving northward.

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It’s not exactly rare for the polar vortex to stretch in the winter.

Generally, the phenomenon happens about once every two years. But scientists are wondering if stretches are becoming more frequent due to climate change.

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A 2021 report found that climate-change-induced sea ice melt in the Arctic appears to be linked to disruptions in the polar vortex.

But more research is needed to understand the full relationship between these complex systems.