Are The Chicago River And Lake Michigan Smoking? Not Really
CHICAGO (CBS) -- Photographers have been having a field day along the lakefront and Chicago River, capturing images of the swirling mist over the water, known as sea smoke or frost smoke.
It might be called smoke, but it's just water vapor.
National Weather Service meteorologist Amy Seeley said, when warm water on the river or lake evaporates into the colder air above, it condenses into wispy fog called sea smoke.
"Right now our lakefront, or at the Chicago River, the water's still warmer, and we've got this cold Arctic air over us. We really have pretty light winds when this happens" she said.
Seeley said, under the right conditions, the chill air above the warmer water becomes saturated with more water than it can hold.
"So the water cools below the dew point. It can't hold any more water vapor, and so all that excess moisture condenses out, so it looks like steam," she said. "It literally looks like -- from the surface of the water -- that you have steam coming up, or that it's being pulled upward. It looks really cool. It's actually like my favorite fog."
She said sea smoke arises from the same process as steam rising from a kettle of boiling water; the only difference being steam is hot, and sea smoke is as cold as the winter chill.
"If you put your hand over it, with steam you would definitely feel it. You're not going to feel that over the lake, per se. It doesn't carry that same amount of heat to it. Just you're seeing the vapor coming off of it. So that's what it looks like, but it won't have the temperature of it," she said.
Seeley said there are lots of forms of fog from which to choose.
"There's advection fog, radiation fog, you have upslope fog, precipitation fog; so there's a few different ones," she said.
Seeley said conditions for sea smoke will continue to be ideal over the next few days, with wind chills dropping as low as 35 below zero Tuesday and Wednesday night.
"Our coldest air is probably going to be arriving tonight, going through Thursday," she said.