If it seems like January is relentlessly gray, you’re not imagining it. (Patty Wetli / WTTW News)

If Chicago seems especially bleak in January, that’s because it is. According to climatic data, the skies typically are only clear in Chicago for seven out of January’s 31 days.

As dreary as that seems, it’s kind of par for the course. 

December in Chicago isn’t really any brighter, but the holidays, and their twinkling lights, go a long way toward masking the gloom. March, as we’ve long suspected, is truly a winter month in spring’s clothing, tied with November for the dubious distinction of fewest clear days. Not for nothing is Chicago’s signature sculpture named Cloud Gate.   

Labeling any one month “the worst” is kind of like choosing which tooth you’d rather have pulled, said Paul Sirvatka, professor of meteorology at the College of DuPage.

“Would you rather have your upper teeth removed or your lower? You’re still going to the dentist,” he said. “Chicago winters are pretty oppressive.”

According to Sirvatka, much of the blame for Chicago’s relentless winter cloud cover can be placed on New Orleans.

The way he explains it, cold dense air hovers over Chicago in the winter. As lighter, warmer air flows up from the Gulf of Mexico, it rises through that blanket of cold, and as it does so, its moisture condenses along the way. And that’s how clouds are born. 

Here’s the rub: For the sun to come out and play in the winter, Chicago needs a high pressure system to swoop in and turn winds from the south to the north. The drier arctic blast — blame Canada — eliminates the issue of rising, cloud-causing, moist, warm air. And lo, the sun appears, but the temperatures drop.

It’s a Catch-22, Sirvatka said: “In the winter, the colder it is, the sunnier.”

Colder temperatures on Thursday let the sun shine through, however briefly, as seen from the WTTW studio. (Patty Wetli / WTTW News)

Contact Patty Wetli: @pattywetli | (773) 509-5623 |  [email protected]