Bogged down in fog: Why Chicago looks, feels like it’s in the clouds

Written By Sun-Times Wire Posted: 06/25/2014, 07:50pm

Summer arrived, officially, days ago. But that mighty cold winter is still leaving its mark.

Yes, you can blame the polar vortex, at least in part, for the fog that keeps rolling in, sliding between skyscrapers at all hours of the day, hugging the lake.

It’s like San Francisco around here. Or London. Except it’s not (see below).

“Part of the issue is that Lake Michigan remains cooler than usual,” said Frank Strait, senior meteorologist for AccuWeather, which is based in State College, Pennsylvania. “Some waters out there are still pretty chilly, especially up north in the lake. [Wednesday] morning it was pretty foggy in Chicago for a while there with the wind coming off the lake.”

Dense Fog Covers Chicago's Willis Tower

The water temperature at the south buoy, which sits in the middle of Lake Michigan due east of Racine, Wisconsin, was 46 degrees Fahrenheit, said Ben Deubelbeiss, a meteorologist with the National Weather Service in Romeoville. Water temperatures closer to shore near Chicago are in the mid to upper 60s.

The main reason for the fog is an intensely moist air mass, where dewpoints are in the the mid to upper 60s, moving over the area, he said. “When it moves over the cooler lake waters, it leads to saturation and fog development.

“We’ve been in a pattern the last couple of weeks that’s been defined by this really moist dewpoint air,” Deubelbeiss said. “It comes from the Gulf of Mexico. It’s not unusual for this to happen, and it’s more common earlier in the season when the lake is cooler.”

Morning fog tends to burn off soon after sunrise farther from the lake, but “when it cools at night, cold air from the lake spills out over land; there’s no warmer air impeding its progress,” he said, so fog blankets the suburbs as well.

As for the San Francisco comparison? “It’s a marine fog in San Francisco, coming from the water onto the land, so it’s similar that way,” Deubelbeiss said, but Chicago won’t experience fog with the same regularity.

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“We have a big warm-up this weekend starting Friday with some warmer temps in the mid-80s,” Deubelbeiss said. “Saturday and Sunday we should have mid to upper 80s, and we may see some 90s in the area Sunday. That will give us more of a summertime feel.”

Strait said Chicago is not the only lakeside city experiencing heavy fog.

Muskegon, Michigan, on the eastern shore of Lake Michigan, has been seeing fog recently, Strait said. “And Duluth, Minnesota, has been socked in every morning. They’ve had east-northeast wind for the past few days and really dense fog and drizzle there. Lake Superior is still really cold — in the 30s.”

Is it foggy in London? Doubtful.

Contrary to the stereotype, it’s not an everyday occurrence in that English city. A December day spurred lots of photos as residents rushed to capture the skyline ensconced in fog. And in March, there was another blanket of fog episode.


The pea-soup variety “fog” common for centuries in London was smog from coal soot and debris that would combine with the moist air. The deadly fog of 1952 prompted stricter environmental regulations that helped clean the air there and in other cities as people took a new look at pollution and how to prevent it.

Want to know more about fog? Check here and here.