REGIONAL—Nine-banded armadillos have expanded their range into central Illinois, marking one of the more visible signs of how climate change is altering the Great Lakes region, according to a new scientific assessment released by the Environmental Law and Policy Center.
The 2025 update, authored by 13 researchers from universities across the Great Lakes basin, documents widespread changes across the region’s climate, ecosystems, and communities. Mean annual temperatures during 2017-2024 were 1.1 degrees F warmer than the previous three decades and 2.5 degrees F warmer than the early 20th century baseline. Since 1951, annual average air temperatures have increased by 2.9 degrees F in the region.
Lakes Michigan, Huron, Erie, and Ontario all experienced record-high average surface temperatures in 2024, following warm fall and winter conditions. Meanwhile, Lake Superior’s summer temperatures increased by 4.8 degrees F from 1979 to 2023, the largest increase among the Great Lakes.
The warming extends into deeper waters, where researchers have documented the most significant temperature increases. New analyses of Lake Michigan’s deep waters show not only that they are warming, but that winter effects in deep waters are diminishing, with changes in the timing and duration of fall overturn and winter cooling affecting the lake’s ecosystem.
Ice coverage across the Great Lakes has declined substantially. In 2024, annual maximum ice cover reached only 16 percent, marking the lowest average ice cover on record within the 52-year observation period from 1973-2024.
This decline affects communities and businesses that have historically depended on lake ice. Many fishing and outdoor sports businesses in the region rely on solid ice conditions, and some fish species use ice for protection from predators during spawning season.
The changing climate is driving species northward. A study found that 29 percent and 33 percent of previously existing populations of cisco and lake whitefish, respectively, have been lost from Wisconsin inland lakes, with the loss of suitable cold-water habitat as a major factor.
Lake whitefish face particular challenges. Stock assessment models predict the species may disappear from some Lake Michigan locations within five years, with warming winters reducing ice cover that is essential for protecting eggs.
Challenges to people
The changes pose new challenges for the 40 million people living in the Great Lakes region. In urban areas like Chicago, cumulative hours above 95 degrees F during summer are projected to increase from 30 hours in 2018-2024 to more than 200 hours in the mid-2030s under high emission scenarios.
Disease-carrying ticks are expanding their range northward. Michigan officials discovered Asian longhorned ticks in 2025, an invasive species that can spread disease among wildlife, domestic animals, and pets. The species reached the United States in 2017 and has since spread to 21 states, including Indiana and Ohio.
Future projections
The report’s projections vary significantly based on future greenhouse gas emissions. Under high-emission scenarios, the Great Lakes basin could warm by 7.4-9 degrees F by the end of the century, while lower emissions would limit late-century warming to 3.2-4.9 degrees F.
Days with maximum temperatures above 90 degrees F are likely to increase by 60 days under high scenarios versus 30 days under lower scenarios, while days below 32 degrees F are expected to decrease by 45-55 days under high scenarios and 25-35 days under lower scenarios.
The Great Lakes contain about 20 percent of the world’s surface freshwater and support the economy and communities of the region. The report’s authors emphasize that continuing to monitor and understand these changes is important for developing adaptation strategies and building resilience in the region.