Monthly Water Level Bulletin for the Great Lakes and Montréal Harbour

Information for the monthly bulletin prepared by the Canadian Hydrographic Service. LEVELnews, a newsletter published by Environment Canada, is included with the bulletin.

On this page

This PDF contains a series of line graphs showing monthly water level data for the Great Lakes and Montréal Harbour. The raw data is also found on the web pages in this section.

Gauging stations network

A network of gauging stations on both sides of the border on each lake is used to determine the average water level for the month. The following stations are used.

  • Lake Superior
    • Duluth
    • Marquette
    • Michipicoten
    • Thunder Bay
    • Point Iroquois
  • Lakes Michigan/Huron
    • Ludington
    • Thessalon
    • Milwaukee
    • Tobermory
    • Harbor Beach
    • Mackinaw City
  • Lake Ontario
    • Toronto
    • Oswego
    • Cobourg
    • Kingston
    • Rochester
    • Port Weller
  • Lake St. Clair
    • Belle River
    • St. Clair Shores
  • Lake Erie
    • Toledo
    • Cleveland
    • Port Stanley
    • Port Colborne
Monthly Bulletin prepared by the Canadian Hydrographic Service Fisheries and Oceans Canada

Water level advisory

Water levels for Lake Michigan-Huron, Lake St. Clair, Lake Erie are:

  • above the level of chart datum
  • above the average level for this time of year

Water levels for Lake Superior, Lake Ontario and Montréal Harbour are:

  • above the level of chart datum
  • below their all-time average for this time of year

Mariners should exercise extreme caution throughout the entire system. This is especially important during periods of strong winds when water levels can rise or fall significantly in a short period of time.

Water level monthly means

The monthly mean levels for the previous year and current year shown on the following charts are the average of water levels recorded at a network of gauging stations on each lake. Historical data from these networks are used to determine the all-time average and the historical extreme monthly levels.

Water levels for the Canadian stations in the networks are collected by the Canadian Hydrographic Service. The probable range of future levels for 6-month forecasts are prepared under the auspices of the International Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data by:

  • Environment Canada
  • the Detroit District, Corps of Engineers

Additional information on water levels in the Great Lakes system may be obtained by contacting the Canadian Hydrographic Service by:

Water level charts

The charts show the water levels in metres relative to chart datum and to International Great Lake Datum (1985).

Water level table

The charts reflect monthly mean water levels in metres referred to International Great Lake Datum (1985).

Monthly Mean Water Levels in metres referred to IGLD 1985
June 2024 Lake Superior Lake Huron Lake St. Clair Lake Erie Lake Ontario Montréal
Mean for Month (preliminary data) 183.44 176.66 175.46 174.62 74.94 6.39
Mean for month last year 183.68 176.68 175.46 174.60 75.24 6.51
Mean for month, last 10 years 183.64 176.89 175.62 174.75 75.25 6.88
Statistics for period of record 1918-2023 1918-2023 1918-2023 1918-2023 1918-2023 1967-2023
Maximum monthly mean / year 183.84
Mean for month, All Time 183.46 176.57 175.21 174.37 75.07 6.68
Minimum monthly mean / year 182.85
Probable mean for next month 183.54 176.70 175.44 174.60 74.92 6.31
Chart Datum 183.20 176.00 174.40 173.50 74.20 5.55