Wisconsin just came off its warmest year on record. In 2024, the statewide average temperature hit 47.6°F, nearly 4 degrees above normal and topping the previous record of 47.4°F set in 2012. If you’ve noticed that winters feel milder, summers feel hotter, and the seasons seem shifted, you’re not imagining it. Several overlapping forces are driving Wisconsin’s warming trend.
2024 Set a New Statewide Record
Wisconsin’s average temperature in 2024 reached 47.6°F, surpassing every year in records going back to 1895. That 3.8-degree departure from the 1991-to-2020 normal isn’t a small blip. It reflects a pattern that’s been building for decades, with the two warmest years in state history now occurring within 12 years of each other.
The winter of 2024-2025 continued the trend. At the La Crosse Regional Airport, temperatures averaged 25.2°F from late December through mid-March, which was 4.2°F warmer than the long-term average dating back to 1872. Average highs ran nearly 5 degrees above normal. On March 14, La Crosse hit 80°F, the third-warmest reading ever recorded during an astronomical winter. Cold still showed up in bursts (Black River Falls dropped to minus 28°F in February), but the overall season leaned unmistakably warm.
How Jet Stream Shifts Bring Milder Air
One short-term driver is El Niño, the periodic warming of Pacific Ocean surface waters that reshapes weather across North America. During an El Niño phase, the polar jet stream shifts northward. That matters for Wisconsin because the jet stream normally acts as a boundary, funneling cold Arctic air southward into the upper Midwest. When it migrates north, those cold intrusions become less frequent and less intense, letting above-average temperatures settle over the northern U.S.
El Niño also redirects the Pacific jet stream across the southern United States, pulling moisture and storm energy away from the central part of the country. The result for Wisconsin is often a winter that’s both warmer and drier than usual. This pattern doesn’t guarantee every day will be mild, but it tilts the odds so that warm stretches last longer and deep-freeze episodes are shorter.
Long-Term Warming Is Reshaping the State
Beyond year-to-year weather cycles, Wisconsin is warming as part of a broader climate shift. Projections from the Wisconsin Initiative on Climate Change Impacts estimate that by 2050, the number of days above 90°F will triple. Winter warming is projected to be even more dramatic, with increases of 5 to 11°F during cold-season months. That range means Wisconsin winters could feel fundamentally different within a generation.
The USDA confirmed part of this shift in 2023 when it updated its Plant Hardiness Zone Map for the first time in over a decade. About half the country, including portions of Wisconsin, moved into the next warmer half-zone. That shift reflects 0 to 5 degrees of warming in minimum winter temperatures measured between 1991 and 2020. For gardeners, it means plants that once couldn’t survive a Wisconsin winter now can. For everyone else, it’s a concrete marker that the baseline climate has changed.
Disappearing Lake Ice
The Great Lakes play a major role in Wisconsin’s climate, and they’re changing too. Between 1973 and 2010, ice coverage on Lake Superior declined by 79 percent. Lake Michigan saw a 77 percent drop over the same period. Less ice means the lakes absorb more solar energy through open water during winter, which in turn warms the air passing over them before it reaches Wisconsin’s shoreline communities.
The feedback loop compounds over time. Warmer water produces less ice the following winter, which means even more heat absorption the next year. For lakeside cities like Milwaukee, Green Bay, and Superior, this contributes to milder winters and can also fuel heavier lake-effect precipitation when cold fronts do push through.
Urban Heat Adds to the Effect
If you live in Milwaukee or Madison, you may feel the warmth more intensely than someone in a rural area. Cities concentrate heat-absorbing surfaces like asphalt, concrete, and dark rooftops that soak up solar energy during the day and radiate it back at night. A 2022 heat-mapping campaign by the Wisconsin DNR found a 10-degree difference on summer evenings between the hottest and coolest parts of Milwaukee, with the most built-up neighborhoods running significantly warmer.
This urban heat island effect doesn’t cause the broader warming trend, but it amplifies it where most people live. Neighborhoods with less tree canopy and more pavement consistently run hotter, which means relief from summer heat is unevenly distributed across the city.
Why It Feels Like More Than a Fluke
What makes Wisconsin’s current warmth so noticeable is that multiple factors are stacking on top of each other. El Niño nudges temperatures upward in any given year. Long-term climate warming raises the baseline that those nudges build on. Declining Great Lakes ice removes a natural cooling influence. And urban development concentrates heat where population is densest. Each factor alone might feel subtle. Together, they produce the kind of warmth that breaks 130-year-old records and makes longtime residents say the weather just isn’t what it used to be.
The data backs up that instinct. Wisconsin’s winters are warming faster than its summers, which is consistent with projections for the upper Midwest. The shift is already measurable in ice cover, planting zones, and temperature records, and climate models project it will accelerate through mid-century.