CHICAGO — Monday morning, Loop commuters snapped pictures and video of steam rising off the Chicago River, a common sight on chilly mornings in the city.
The vapor is called "sea smoke" or "steam fog," said Amy Seeley, a meteorologist for the National Weather Service.
The phenomenon happens to bodies of water when the water temperature is higher than the air temperature above.
The water creates moist, warm air above its surface, and when that air mixes with the colder, dryer air a bit higher, the moist air cools and condenses, forming vapor, according to the National Weather Service. The vapor then looks like smoke, or steam, rising off the water's surface.
You'll notice "sea smoke" is always a few inches or feet above the surface, according to USAToday.
Kyla Gardner talks about "sea smoke:"
Monday morning in Chicago, the air temperature was around 3 below zero, much colder than the still-moving, and therefore above-freezing, river.
"It's not unusual," Seeley said of sea smoke. You can see the steam during the rest of the week, as temps are expected to remain in the single digits or below freezing. Eventually, though, the Chicago River will freeze.
A photo posted by Maralyn Owen (@nylaramo) on
Steam rising from Chicago river on a frigid morning. pic.twitter.com/1EKP1RSh7w
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