When Chicago sank to −23°F (about −31°C) on 30 January 2019, Lake Michigan looked as if it were boiling. Thick white vapour drifted off the open water, slabs of ice crowded the shoreline and the downtown skyline stood behind a curtain of frozen haze. The scene had a simple cause: the air over the city had become far colder than the lake beneath it, and the lake was giving its warmth and moisture away faster than the air could hold it.
The photographs and clips below were taken by residents, airline passengers and news crews during the two coldest days of that cold wave. Below them you will find what the thermometer actually read, why the lake "steamed", what the glittering "diamond dust" was, and how to enjoy a sight like this without taking risks on lake ice.
What was happening on the lake
Steam fog, also called sea smoke or frost smoke, forms when very cold air moves across water that is comparatively warm. A thin layer of air directly above the surface picks up moisture and is warmed slightly. When the bitter air above mixes with it, that layer cools past its dew point and the extra vapour condenses into tiny droplets, exactly the way breath clouds on a winter morning or a mug of tea smokes in a cold kitchen.
Lake Michigan is huge and deep, with an average depth of around 85 metres (279 feet), so it loses its summer heat slowly. In late January much of its open water was still just above freezing, while the air over it was roughly 50°F (nearly 30°C) colder. That enormous contrast is why the vapour rose in rolling, wind-driven columns rather than as a light morning mist. Sea smoke is common in the Arctic and Antarctic and far less common in temperate cities, which is part of why Chicagoans rushed to their windows with phones.
Ice coats a lakefront breakwater as the skyline fades into frozen haze. Spray thrown up by waves freezes on contact in this kind of cold, building thick, rippled layers on walls, piers and railings. The grey, low-contrast light is typical of days when steam fog drifts inland.
How cold Chicago got in January 2019
The cold came from a lobe of the Arctic polar vortex. A sudden stratospheric warming in late December 2018 and early January 2019 weakened the circulation that normally keeps the coldest air bottled up near the pole, and a piece of it slid south over central Canada and the north-central United States, where it stalled for roughly a week.
- 30 January 2019: O'Hare International Airport fell to −23°F (about −31°C). The wind chill reached about −52°F (−47°C), and the daytime high of −10°F (−23°C) was only a degree above the city's coldest maximum on record.
- 31 January 2019: O'Hare recorded −21°F (about −29°C), a record low for that calendar date.
- Chicago's all-time record of −27°F (about −33°C), set on 20 January 1985, survived.
- Illinois did set a new state record: −38°F (about −39°C) at Mount Carroll on 31 January, beating the −36°F recorded at Congerville on 5 January 1999.
Some early reports gave the 31 January low as −29°C and called it a city record outright; it was a record for that date only. Travel was badly disrupted as well: more than 1,400 flights were cancelled at O'Hare and over 250 at Midway, and several deaths in the Chicago area were linked to the cold.
A lone figure in a red jacket stands on the snow-covered shelf of shore ice, right at the edge of open water, while sea smoke streams across the lake. The contrast shows how thin the line is between solid-looking ice and deep, moving water. It is a striking image, and also a reminder of why officials urge people to stay off lakefront ice.
Diamond dust: the glitter in the air
On the clearest, coldest mornings, some of the moisture in the air froze straight into tiny ice crystals instead of liquid droplets. Meteorologists call this diamond dust. The crystals are usually simple six-sided plates or columns, and as they tumble they catch the sun and sparkle, which is how the phenomenon got its name.
Diamond dust needs temperatures well below freezing and is a familiar sight in polar regions; in the interior of Antarctica it is common below about −25°C. Because the crystals behave like tiny prisms, they can also create sun dogs (bright spots either side of the sun) and light pillars, tall columns of light above street lamps or the low sun. Several Chicagoans photographed these effects during the cold snap.
Seen from above, a frozen stretch of lake becomes a web of pale pressure cracks around a lone marker post, with fog swallowing the horizon. Lake ice is constantly shifting: wind, currents and temperature swings open and refreeze these seams, so ice that looks continuous can vary hugely in thickness from one step to the next.
The lake from apartments, newsrooms and the air
Social media filled with views of the lake during those two days. Sports-business reporter Darren Rovell shared a picture taken from a lakefront apartment by the account @reallyhalalfood, showing open water steaming beneath a pale sun.
A view of Lake Michigan with the air temperature at -20 degrees from an apartment on the water in Chicago yesterday (📷 by @reallyhalalfood) pic.twitter.com/izgoyenUqr
— Darren Rovell (@darrenrovell) January 31, 2019
The British newspaper The Independent shared footage of the lake under its ice and vapour.
Lake Michigan freezes over, creating spectacular views pic.twitter.com/8DDjRkgFW7
— The Independent (@Independent) January 31, 2019
One of the most widely shared images was taken from an aircraft. David Funk posted the view his brother captured while landing on one of the few flights still reaching Chicago, showing the city edged by a broad apron of broken ice.
My brother was on one of the few flights into Chicago this morning. He took this photo of frozen Lake Michigan from the plane. pic.twitter.com/cS8XRCTPQV
— David Funk (@DavidPFunk) January 30, 2019
Three further posts from residents, by John Gordon, CrazyCatLady9 and Tina Jensen, showed the lake from apartment windows and the beachfront. Those posts have since been removed from X, but their wording is preserved below for the record.
View of Lake Michigan from my apartment. One of the more awe-inspiring sights I’ve seen in my two years in Chicago pic.twitter.com/ERH0xebgPx
— John Gordon (@John_W_Gordon) January 30, 2019
(This post is no longer available on X.)
@weatherchannel You know it's cold when Lake Michigan freezes - MORE PICS. pic.twitter.com/C4zcw9mi4n
— CrazyCatLady9 (@CrazyCatMommy9) January 30, 2019
(This post is no longer available on X.)
Anyone want to go to the beach? Frozen Lake Michigan in #Chicago. pic.twitter.com/TF6AZgaNeP
— Tina Jensen (@TinaRJensen) January 29, 2019
(This post is no longer available on X.)
Video of the steaming lake
Video gives a better sense of how fast sea smoke moves. In these clips the vapour races across the surface with the wind and curls upward in columns, sometimes many metres tall.
ABC7 Chicago covered the cold wave across the region, from the lakefront to the commute.
Does Lake Michigan freeze over?
Despite headlines saying the lake "froze over", it did not freeze from shore to shore in 2019. Ice formed along the shoreline, in harbours and in sheltered shallows, while large areas of open water remained, which is precisely why the lake could steam. The Great Lakes do develop extensive ice in severe winters and shipping largely stops, but Lake Michigan's size and depth make total ice cover rare.
That matters for safety. Shore ice is built from wave-piled slush and broken plates; it can hide air pockets and overhangs, and the boundary with open water moves. If you want to see a winter lake like this:
- Watch from the shore, a pier with railings or a high window rather than walking out on lakefront ice.
- Protect exposed skin. At wind chills near −50°F, frostbite can develop on bare skin within minutes.
- Go early on a clear, calm morning. Steam fog and diamond dust are usually most dramatic around sunrise, when the air is at its coldest.
- Keep phones warm in an inner pocket; batteries drain quickly in deep cold.
Cold snaps like January 2019 are brief, but they turn a familiar city lake into something closer to the Arctic Ocean for a few days. The images above are a record of that moment, and a good lesson in the physics of water and air.
Sources: ABC7 Chicago: polar vortex temperatures and the Illinois state record; Wikipedia: January–February 2019 North American cold wave; Wikipedia: Sea smoke (steam fog); Wikipedia: Diamond dust; Wikipedia: Lake Michigan; Darren Rovell on X (photo by @reallyhalalfood); David Funk on X.
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