Chicago cold spell brings ice to Lake Michigan 

Today’s Image of the Day from NASA Earth Observatory features ice on Lake Michigan in late January 2025, when extreme cold settled into the Chicago area.

“Between January 19 and 24, 2025, a brutal cold snap hit Chicago. This satellite image captured a glimpse of the wintry aftermath,” noted NASA.

According to the National Weather Service (NWS), the first half of the cold spell was the most intense. 

Cold spells and snowfall

Cold spells in the Chicago area are often accompanied by strong winds and significant snowfall.

“On January 21, the air temperature in Chicago reached as low as minus 15 degrees Fahrenheit (minus 26 degrees Celsius). At the time, little to no snow covered the ground in Chicago, which NWS noted is uncommon amid sub-zero temperatures,” said NASA.

“Snowflakes returned toward the end of the cold spell. Between the mornings of January 22 and 23, several waves of snowfall produced the blanket of white across the Chicago area visible in this image.”

“Another expanse of white is visible atop Lake Michigan. This is lake ice, which grows on the Great Lakes each winter, though its extent and timing can be highly variable. Ice coverage on the Great Lakes typically reaches its annual peak in late February or early March.”

Visible ice patterns

Jia Wang, an ice climatologist at NOAA’s Great Lakes Environmental Research Laboratory (GLERL), noted that on January 24, winds were blowing offshore and pushing ice away from the coastline.

In the photo, areas of dark, thin ice can be seen close to the shore, while patchy areas of bright white ice are visible away from shore. According to Wang, the whiter areas might be due to ice that has piled up and formed a very rough surface.

Ice cover on Lake Michigan 

“The area of Lake Michigan covered with ice in late January 2025 hovered around the historical average (1973-2024) for the time of year, according to data from GLERL. When the image was acquired, ice covered about 20 percent of the lake,” noted NASA.

“Meanwhile, several hundred miles to the east, ice on Lake Erie spiked well above average in late January, according to GLERL, with ice spanning around 80 percent of the lake. The ice was thick enough to temporarily immobilize a Canadian cargo freighter, according to news reports.”

To calculate the thickness of ice on the Great Lakes, experts are investigating ways to use altimetry data from NASA’s ICESat-2 (Ice, Cloud and land Elevation Satellite-2).

Eric Anderson, a researcher at the Colorado School of Mines, noted that such measurements could improve ice and weather forecasting as well as help us understand changes in Earth’s surface freshwater.

Ice on the Great Lakes

Ice formation on the Great Lakes is a dynamic process influenced by seasonal temperatures, wind patterns, and climate variability. 

Each year, ice begins to develop in late fall and early winter, typically forming first in sheltered bays and shallow areas before extending over deeper waters. 

The extent and duration of ice cover vary significantly, with some years experiencing widespread freezing while others see only partial coverage due to warmer conditions.

Fluctuations in ice coverage

Historically, ice coverage on the Great Lakes has fluctuated, with long-term records showing a decline in ice extent due to rising global temperatures. 

The lakes act as vast heat reservoirs, meaning their large thermal mass can delay freezing, especially in milder winters. 

When ice does form, it affects local weather patterns, contributing to lake-effect snow in surrounding regions. It also impacts ecosystems, as ice cover influences fish spawning, winter survival of aquatic organisms, and shoreline erosion.

Increasing variability in ice cover 

In recent decades, scientists have observed increasing variability in ice cover, with some years experiencing near-record lows. 

This trend impacts commercial shipping in two key ways: reduced ice cover can extend the navigational season, but unpredictable freeze-thaw cycles make ice-breaking operations more challenging.

Additionally, ice conditions influence recreational activities such as ice fishing, skating, and snowmobiling – all of which depend on stable and thick ice.

Overall, ice on the Great Lakes is a key indicator of changing climate patterns, with its variability providing insights into broader environmental shifts. 

The image was captured on January 24, 2025 with the OLI (Operational Land Imager) on Landsat 8.

Image Credit: NASA Earth Observatory 

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