The Canadian Hydrographic Service
Hourly water levels for Lake Ontario and the St. Lawrence River

Great Lakes Levels Home Page
1, 2 & 3 month levels, forecasts, bi-monthly connecting channel forecasts (including the St. Lawrence River) from the U.S. Army Corps of Engineers.

NOAA-NOS Center for Operational Oceanographic Products &Services

International St. Lawrence River Board of Control
Daily (posted weekly late Thursdays or Fridays) levels for Lake Ontario and St. Lawrence River down to Sorel. Daily outflows & upcoming weekly outflows.

Great Lakes Basin Hydrology
Monthly precipitation for each of the Great Lakes & total basin.
Monthly supplies and outflows for each of the Lakes.

International Joint Commission home page.

Great Lakes Boating Federation