Lake Erie algal blooms could be visible by mid-July

OHIO — The National Oceanic Atmospheric Administration’s National Centers for Coastal Ocean Science predicts that western Lake Erie’s algal blooms will be moderately harmful. It’s expected to measure 3.5 on the HAB (cyanobacterial harmful algal blooms) severity index, with a potential range of 3 to 4.5.

The severity index is based on the bloom’s amount of algae, according to Ohio State University, during the peak 30 days of the bloom. Anything between a 3 to 5 is considered a moderate bloom, whereas an index above 5 indicates more severe algal blooms. 

A bar graph of the 2026 predicted bloom severity for Lake Erie as compared with previous years. The wide orange bar at right is the likely range of severity for this season, based on the limits of the forecast uncertainty (3-4.5; moderate bloom). (NOAA/Heidelberg University/University of Michigan/NCSU)

Experts from NOAA and other agencies discussed the seasonal forecast late last week, stating they expect to see a visible bloom in mid-July. 

Much of the bloom will be set in the western basin. The central basin is usually unaffected until later in the season, but some localized blooms could occur around some of the rivers after rainstorms.

“Toxic algae affect not only the health of people and Great Lakes ecosystems, but they can negatively impact local and regional economies by preventing people from fishing, swimming, boating and visiting the shoreline,” said Nicole LeBoeuf, assistant administrator for NOAA’s National Ocean Service. “NOAA’s Lake Erie harmful algal bloom forecast is designed to provide timely, science-based information to water managers and public health officials as they make decisions to protect their communities and visitors.” 

HABs have a blue-green algae called cyanobacteria, which is capable of producing a toxin called microcystin. It’s a liver toxin that can cause harm to human and wildlife health, according to OSU. While it impacts health, it also impacts local governments and economies. Cities tend to add more treatment to drinking water, as well as close beaches and other areas, which can prevent people from fishing, swimming, boating and just visiting. 

NOAA said it will issue a seasonal forecast update in late July. 

More information on predictions and visualizations can be found here.