Köppen climate types in Wisconsin showing most of the state to be warm-summer humid continental.
Köppen climate types in Wisconsin showing most of the state to be warm-summer humid continental.

Climate change in Wisconsin encompasses the effects of climate change, attributed to man-made increases in atmospheric carbon dioxide, in the U.S. state of Wisconsin.

According to the United States Environmental Protection Agency, "Wisconsin's climate is changing. In the past century, most of the state has warmed about two degrees (F). Heavy rainstorms are becoming more frequent, and ice cover on the Great Lakes is forming later or melting sooner. In the coming decades, the state will have more extremely hot days, which may harm public health in urban areas and corn harvests in rural areas".[1]

Environmental impacts

Heavy precipitation and flooding

"Changing the climate is likely to increase the frequency of floods in Wisconsin. Over the last half century, average annual precipitation in most of the Midwest has increased by 5 to 10 percent. But rainfall during the four wettest days of the year has increased about 35 percent. During the next century, spring rainfall and annual precipitation are likely to increase, and severe rainstorms are likely to intensify. Each of these factors will tend to further increase the risk of flooding".[1]


"Changing the climate is likely to shift the ranges of plants and animals. For example, rising temperatures could change the composition of Wisconsin’s forests. As the climate warms, the populations of paper birch, quaking aspen, balsam fir, and black spruce may decline in the North Woods, while oak, hickory, and pine trees may become more numerous. Climate change will also affect habitat for animals such as fish. Rising water temperatures will increase the available habitat for warmwater fish such as bass, while shrinking the available habitat for coldwater fish such as trout. Declining ice cover and increasingly severe storms would harm fish habitat through erosion and flooding".[1] Climate change is also reportedly causing mercury levels to fluctuate in fish caught in Wisconsin lakes, leading to increasingly unsafe levels of mercury.[2]

"Warming could also harm ecosystems by changing the timing of natural processes such as migration, reproduction, and flower blooming. Migratory birds are arriving in the Midwest earlier in spring today than 40 years ago. Along with range shifts, changes in timing can disrupt the intricate web of relationships between animals and their food sources and between plants and pollinators. Because not all species adjust to climate change in the same way, the food that one species eats may no longer be available when that species needs it (for example, when migrating birds arrive). Some types of animals may no longer be able to find enough food".[1]

Great Lakes

"Changing the climate is also likely to harm water quality in Lake Michigan. Warmer water tends to cause more algal blooms, which can be unsightly, harm fish, and degrade water quality. Severe storms also increase the amount of pollutants that run off from land to water, so the risk of algal blooms will be greater if storms become more severe. Increasingly severe rainstorms could also cause sewers to overflow into the lake more often, threatening beach safety and drinking water supplies. One advantage of climate change is that warmer winters reduce the number of days that ice prevents navigation. Between 1994 and 2011, the decline in ice cover lengthened the shipping season on the Great Lakes by eight days. The lakes are likely to warm another 3° to 7°F in the next 70 years, which will further extend the shipping season".[1]

Economic and social impacts

Winter recreation

"Warmer winters are likely to shorten the season for recreational activities like ice fishing, snowmobiling, skiing, and snowboarding, which could harm the local economies that depend on them. Small lakes are freezing later and thawing earlier than a century ago, which shortens the season for ice fishing and ice skating. Since the early 1970s, winter ice coverage in the Great Lakes has decreased by 63 percent. The warmer climate is likely to shorten the season when the ground is covered by snow, and thereby shorten the season for activities that take place on snow. Nevertheless, annual snowfall has increased in much of the Great Lakes region, which could benefit winter recreation at certain times and locations".[1]


"The changing climate may reduce the output of Wisconsin's multi-billion-dollar dairy industry, which generates more than half of the state’s farm revenue. Higher temperatures cause cows to eat less and produce less milk. Climate change may also pose challenges for crops, but it could also have some benefits; the net effect is unknown. Longer frost-free growing seasons and higher concentrations of atmospheric carbon dioxide would increase yields of soybeans and wheat during an average year. But increasingly hot summers are likely to reduce yields of corn. Seventy years from now, much of Wisconsin is likely to have 5 to 10 more days per year with temperatures above 95°F than it has today. More severe droughts or floods would also hurt crop yields".[1]

Air pollution and human health

"Changing the climate can harm air quality and amplify existing threats to human health. Higher temperatures increase the formation of ground-level ozone, a pollutant that causes lung and heart problems. Ozone also harms plants. In some rural parts of Wisconsin, ozone levels are high enough to reduce yields of soybeans and winter wheat. EPA and the Wisconsin Department of Natural Resources have been working to reduce ozone concentrations. As the climate changes, continued progress toward clean air will become more difficult".[1]

"Climate change may also increase the length and severity of the pollen season for allergy sufferers. For example, the ragweed season in Madison and La Crosse is two weeks longer than in 1995, because the first frost in fall is later. The risk of some diseases carried by insects may also increase. The ticks that transmit Lyme disease are active when temperatures are above 45°F, so warmer winters could lengthen the season during which ticks can become infected or people can be exposed to the ticks".[1]

"Northern cities like Milwaukee are vulnerable to heat waves, because many houses and apartments lack air conditioning, and urban areas are typically warmer than their rural surroundings. For example, heat waves killed 91 people in Milwaukee County in 1995, and 11 people in 1999. Heat stress is likely to increase as climate change brings hotter summer temperatures and more humidity. Certain people are especially vulnerable, including children, the elderly, the sick, and the poor".[1]


In October 2019, Governor Tony Evers created the "Governor's Task Force on Climate Change", which is tasked with issuing recommendations to the governor by August 2020.[3]


  1. ^ a b c d e f g h i j "What Climate Change Means for Wisconsin" (PDF). United States Environmental Protection Agency. August 2016.
  2. ^ Whites-Koditschek, Sarah (June 10, 2019). "Climate Change Causes 'Roller Coaster' Mercury Levels In Wisconsin Fish". Wisconsin Public Radio.
  3. ^ State of Wisconsin Office of the Governor (October 17, 2019). Executive order #52: Relating to the creation of the Governor's Task Force on Climate Change (PDF) (Report).

Further reading