2025 Great Lakes Water Levels Fall Below Last Year’s Mark Despite Seasonal Rise

Unseasonably cold nights and shifting outflows influence 2025 Great Lakes water levels, with Michigan-Huron showing the sharpest annual drop.

Cold May Temperatures and Mixed Rainfall Mark the Week

The latest report from the U.S. Army Corps of Engineers Detroit District reveals that despite the typical spring rise in Great Lakes water levels, most lakes are still running below last year’s levels as of May 23, 2025. While northern Michigan and Ontario experienced near-freezing overnight lows, parts of the central basin were hit with heavy rainfall and localized flooding from early week storms.

The week’s weather across the Great Lakes basin saw a wide swing in temperatures—from the 30s in the Upper Peninsula to the 70s in the southern basin. Looking ahead, the forecast calls for warmer conditions and limited rainfall, potentially moderating the seasonal water level rise.

2025 Great Lakes Water Levels Trending Higher This Month, But Lag Behind 2024

Water levels across all five Great Lakes have risen 4 to 7 inches over the past month, part of the normal spring cycle. However, the year-over-year comparison tells a more complicated story.

• Lake Superior is down 2 inches from May 2024.
• Lake Michigan-Huron, which includes Michigan’s Thumb and shoreline communities, has dropped 8 inches from last year’s levels.
• Lakes St. Clair and Erie are also below 2024’s levels by 5 and 4 inches, respectively.
• Lake Ontario is the only exception, sitting 2 inches above its May 2024 mark.

The decline is most pronounced in Lake Michigan-Huron, which affects thousands of miles of Michigan shoreline and ports. These reductions can influence everything from marina operations to shipping capacity and shoreline erosion.

Current Levels Compared to Long-Term Averages Offer a Mixed Picture

Notably, the May 23 measurements for Lakes Superior and Michigan-Huron remain below their long-term monthly averages by 2 to 4 inches. In contrast, Lakes St. Clair and Erie are trending above average—by 4 and 6 inches respectively—while Lake Ontario is hovering near its May norm.

Here’s a snapshot of 2025 Great Lakes water level changes compared to long-term May averages:

• Superior: -2 inches
• Michigan-Huron: -4 inches
• St. Clair: +4 inches
• Erie: +6 inches
• Ontario: 0 inches

While this doesn’t trigger any emergency action, it underscores how variable lake levels can be depending on both precipitation and outflow conditions.

Forecast Points to Modest Water Level Changes by Late June

The next 30 days are expected to bring minor changes:

• Lakes Superior, Michigan-Huron, and Ontario will likely rise by 2 to 3 inches.
• Lake St. Clair is expected to hold steady.
• Lake Erie may see a slight decline of 1 inch.

According to the Army Corps, Lake Superior’s outflow into the St. Marys River is projected to be below average for May, while outflows from Michigan-Huron, St. Clair, and Erie are expected to be above average. These discharge patterns impact lake levels and should be monitored closely by mariners and shoreline businesses.

Mariners and Shoreline Users Urged to Check Local Levels

The Corps advises that all listed measurements reflect still-water elevations across entire lake surfaces. However, local variations due to wind, storm surges, or seiches may impact mariners and harbor operations.

Users of the St. Marys, St. Clair, Detroit, Niagara, and St. Lawrence Rivers are particularly advised to consult navigation charts and real-time water level readings.

Find official data and updates through the Detroit District of the U.S. Army Corps of Engineers, NOAA’s Great Lakes operational ocean data services, or the Great Lakes Information Network.

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