May 2026 Water Level Update

Following Wisconsin’s wettest April on record, Lake Michigan water levels continued their seasonal rise, increasing 4 inches from April to May. Lake Michigan is now 2 inches above the long-term average water level for May. This is the first time Lake Michigan has been above the long-term average water level since September 2024. Water levels are forecast to increase another 3 inches in June.

Water Levels on Lake Michigan-Huron

Here are 5 things to know about water levels on Lake Michigan for May 2026.

What are the current water levels on Lake Michigan?

The water level of Lake Michigan as of May 22, 2026 was at an elevation of 579.27 feet above sea level (from the International Great Lakes Datum). To put this level into perspective, here are some statistics for Lake Michigan relative to the period of water level records measured from 1918 to present (statistics from USACE’s Weekly Water Level Update).

What is the outlook for future water levels?

Water levels continued their seasonal rise in April and May. The USACE 6-month forecast of Great Lakes Water levels shows water levels are expected to continue their seasonal rise through July or August, with water levels continuing to be above the long-term average (see the water level forecast issued for May 2026 below).

USACE six-month water level forecast for Lake Michigan-Huron retrieved for May 2026 from: https://water.usace.army.mil/office/lre/docs/mboglwl/MBOGLWL-mich_hrn.pdf

What are current and predicted climate conditions like?

According to NOAA’s Climate Prediction Center, El Niño conditions are likely to emerge soon (82% chance in May-July 2026) and continue through winter. Across Wisconsin, there are equal chances for above or below normal temperatures in June. Precipitation forecasts for June show an equal chance for above normal or below normal precipitation in Wisconsin (see precipitation outlook map from NOAA Climate.gov below). Check out the NOAA Climate Prediction Center for a full U.S. climate outlook.

The U.S. precipitation outlook for June 2026. Map by NOAA Climate.gov, based on data from the Climate Prediction Center. From: https://www.cpc.ncep.noaa.gov/

What is behind Great Lakes water level fluctuations?

The story of Great Lakes water level changes is told by Net Basin Supply. Net Basin Supply (NBS) accounts for the water going into a lake in the form of precipitation and runoff minus water leaving a lake due to evaporation of water from the lake surface.

NBS represents the net influence of precipitation over the lake, runoff from a lake’s watershed into the lake, and evaporation from the lake’s surface. Image credit: National Oceanic and Atmospheric Administration

In general, when Net Basin Supply is positive, more water enters the lake than leaves, causing a rise in lake levels. When Net Basin Supply is negative, more water leaves the lake than enters, causing a drop in lake levels. 

The annual peak Net Basin Supply occurs when runoff peaks in the spring and experiences its minimum when over-lake evaporation peaks in the winter. These maximums and minimums in Net Basin Supply correspond to the seasonal water level rise and fall.

Evaporation takes place when the Lake’s surface water temperature is warmer than the air temperature. Evaporation increases in the fall and winter as the difference between air temperature and water temperature increases.

Following Wisconsin’s wettest April on record, Lake Michigan water supplies were more than double average, and water outflows were slightly above average. As a result, water levels on lakes Michigan and Huron had their largest surge for the month of April since record-keeping began in 1918. Water levels jumped by a record 13.4 inches on the lake last month, or triple their average rise of 4.3 inches in April.

How are water levels trending?

Since monthly record highs in 2020, Great Lakes water levels had been trending downwards. In October 2024, Lake Michigan’s monthly mean water level dropped below average for the first time in 10 years and remained below average until this month. The trend has reversed, with May water levels 7 inches higher than they were at the same time in 2025 and 2 inches higher than the long-term May monthly average. Water levels are expected to remain slightly above average for the next six months.

The graph below visualizes the monthly NBS in recent years compared to the monthly mean, maximum, and minimum for each lake basin. Red diamonds represent below average NBS, whereas blue diamonds represent above average NBS.

Monthly NBS in recent years compared to the monthly mean, maximum, and minimum for each lake basin. Retrieved from: https://water.usace.army.mil/office/lre/basinconditions/basinConditions

Water level fluctuation is a process that occurs annually due to changes in net basin supply. For Lake Michigan, January through April 2026 had above average net basin supply, contributing to the seasonal water level increase.

More Resources & Relevant Information:

1. In this Adapting to A Changing Coast PBS Special, Dr. Adam Bechle explains how fluctuations in rainfall, runoff, and evaporation cause the Great Lakes’ water levels and coastlines to vary.
2. NOAA’s Climate.gov site hosts climate data and information to help you understand climate processes and make decisions on how to manage climate-related risks and opportunities.
   • U.S. Climate outlook for June 2026
   • Great Lakes Chapter of the Climate Resilience Toolkit
3. Our Coastal Hazards page for details about the impacts of high water levels, including erosion, flooding, and navigation issues.
4. Our Policy, Planning, and Risk Reduction Strategies page has tools and resources to help local governments identify local resilience opportunities.