"Stratospheric warming events have been increasing in frequency the past decade or so -- possibly related to diminishing sea ice," Marshall said.
That might be linked to climate change, but he cautioned that one week of extreme temperature changes does not equal pinpoint evidence of global warming.
"Weather is to your mood as climate is to your personality. You cannot judge climate by a day or week," he said.
The other factor is a weather phenomenon that circles the world at the equator called the Madden-Julian Oscillation.
"Because the MJO influences (temperature) through tropical rainfall, it can modify weather patterns far away from the equator," Climate Central reported.
In Chicago, people like Corey Lubowich enjoyed a short break from the cold. Lubowich, a 24-year-old theater producer who grew up in the suburbs, said he doesn't ever remember a week like this in January.
"Chicago weather is generally unpredictable, but particularly so this winter," he said.
The other day he walked out of his place bound for the gym wearing just a hoodie and pants. But on Friday, it'll be back to the layer strategy -- T-shirt covered by hoodie covered by thick jacket. And add a scarf, hat and gloves.
Maureen Gribble, who also grew up in Chicago, said she had a friend who just moved there from California and was puzzled by the mild winter.
"I didn't want to burst her bubble," Gribble said.
The stay-at-home mom said she helped her buddy get set up for the real winter.
After all, there is no bad weather, just bad clothing choices.
It looks like Gribble and her family will be bundling up again this weekend when they head up to Wisconsin. It's going to be in the 20s. She hopes there'll be a lot of snow, and Charlie will get a chance to finally jump on that sled.