Wisconsin Climate Shift: Last 25 Years

Temperature Trends: Wisconsin's Warming Climate

Over the past 25 years, Wisconsin has experienced a significant warming trend. Average annual temperatures have increased by approximately 1.6°F between 1979 and 2021, with an overall rise of about three degrees since 1950. This warming is particularly pronounced in autumns and springs, resulting in an extended growing season. Recent years have seen unprecedented warmth, with the winter of 2023-2024 being the warmest on record, and 2024 potentially being Wisconsin's warmest year ever. Nighttime low temperatures have risen more than daytime highs, contributing to overall warmer conditions.

Average Annual Temperature Change (1999-2024)

Precipitation Patterns: A Wetter Wisconsin

Wisconsin has become notably wetter over the last 25 years. Average annual precipitation has risen significantly, with an increase of about 4.9 inches between 1979 and 2021, and an overall increase of about five inches (17%) since 1950. The greatest increases have been observed during the spring and winter months. This has led to periods of "soggy spring" conditions and dramatic reversals of drought, such as in June 2024, which was Wisconsin's third wettest June on record. While overall wetter, precipitation patterns are also becoming more variable, leading to both heavy rainfall events and periods of drought.

Annual Precipitation Variation (1999-2024)

Extreme Weather Events: Increasing Frequency and Severity

The past 25 years have seen a marked increase in the frequency and severity of extreme weather events across Wisconsin. This includes more frequent extreme precipitation events (greater than 2 inches in one day), leading to significant flooding and storm damage. Notably, 2024 experienced an unprecedented series of events, including the state's first-ever February tornadoes (45 tornadoes in total, the third-highest annual amount in state history). Periods of intense rainfall can be followed by deepening droughts, such as the "third-warmest and sixth-driest September on record" in 2024, which contributed to increased wildfire risk and earlier wildfire seasons.

Tornadoes & Severe Storms

  • First-ever recorded February tornadoes in 2024.
  • 45 tornadoes in 2024, third-highest annual amount.
  • Warmer winter temperatures extend tornado season.

Flooding & Drought

  • Increased frequency of extreme rainfall events (over 2 inches/day).
  • Soggy springs and record-wet months (e.g., June 2024, third wettest).
  • Rapid shifts from wet to dry, leading to severe droughts (e.g., October 2024).
  • Mississippi River in La Crosse set flood stage record in June 2024.

Wildfires

  • Over 1,100 wildfires burned 2,500 acres in 2024, above average.
  • Wildfire season starting earlier (e.g., February 2024, snow-free conditions).
  • Dry fall conditions exacerbate fire risk and duration.

Ecosystem Impacts: Changes Across Land and Water

Wisconsin's ecosystems are undergoing significant changes due to climate shifts. Warming temperatures have led to record low ice cover on the Great Lakes (Lakes Michigan and Superior hit historic lows in 2024) and inland lakes like Mendota and Monona, impacting food webs, fisheries, and coastal infrastructure. Increased water temperatures are also contributing to more frequent and larger harmful algal blooms, particularly in Lake Superior, an emerging problem in a lake historically less prone to them. Changes in hardiness zones affect plant and animal life, while fluctuating water levels and eroding bluffs endanger coastal areas.

Key Ecosystem Impact Zones in Wisconsin

Agriculture & Water Resources: Facing New Challenges

The agricultural sector and water resources in Wisconsin are significantly impacted by climate change. Farmers face increased heat stress on livestock and crops, leading to decreased dairy milk production and potential crop losses. Rapid shifts between warm and cold periods in spring can damage fruit crops and soil health. Less reliable winter snow and ice cover threaten alfalfa, winter cereals, and cranberry crops. Increased pest and weed pressure requires new management strategies. Water resources are strained by increased drought risk, leading to higher groundwater withdrawals for irrigation, and conversely, excessive precipitation causes waterlogged soils, delayed planting/harvesting, increased soil erosion, and nutrient runoff.