Water levels forecast

The water levels forecast for Lake Superior, Huron, St. Clair, Erie and Ontario, and Montréal Harbour. Monthly mean water levels are reflective of International Great Lake Datum (1985), which refers to metres above chart datum. Data also references exceedance probability.

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About monthly mean lake levels

The forecast of monthly mean lake levels for the next 6 months are grouped as:

  • high level, where there's a 5% probability of exceeding this level
  • most probable level, where there's a 50% probability of exceeding this level
  • low level, where's there's a 95% probability of exceeding this level

Canada and U.S. flag water levels are collected by the:

  • Canadian Hydrographic Service for the Canadian gauges
  • National Ocean Service and National Oceanic Atmospheric Administration for the American gauges

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 U.S. Army Corps of Engineers, Detroit District
  • Great Lakes-St. Lawrence Regulation Office in Cornwall

Lake Superior

Chart datum 183.20m International Great Lake Datum (1985).

Month 5% Most probable 95%
June 2022 183.61 (0.41) 183.58 (0.38) 183.54 (0.34)
July 2022 183.70 (0.50) 183.62 (0.42) 183.56 (0.36)
August 2022 183.75 (0.55) 183.64 (0.44) 183.56 (0.36)
September 2022 183.77 (0.57) 183.63 (0.43) 183.53 (0.33)
October 2022 183.76 (0.56) 183.60 (0.40) 183.48 (0.28)
November 2022 183.72 (0.52) 183.54 (0.34) 183.40 (0.20)

Lake Huron

Chart datum 176.00m International Great Lake Datum (1985).

Month 5% Most probable 95%
June 2022 176.86 (0.86) 176.82 (0.82) 176.80 (0.80)
July 2022 176.92 (0.92) 176.85 (0.85) 176.78 (0.78)
August 2022 176.94 (0.94) 176.82 (0.82) 176.73 (0.73)
September 2022 176.91 (0.91) 176.78 (0.78) 176.65 (0.65)
October 2022 176.88 (0.88) 176.70 (0.70) 176.56 (0.56)
November 2022 176.84 (0.84) 176.63 (0.63) 176.47 (0.47)

Lake St. Clair

Chart datum 174.40m International Great Lake Datum (1985).

Month 5% Most probable 95%
June 2022 175.55 (1.15) 175.50 (1.10) 175.44 (1.04)
July 2022 175.60 (1.20) 175.50 (1.10) 175.40 (1.00)
August 2022 175.56 (1.16) 175.44 (1.04) 175.32 (0.92)
September 2022 175.52 (1.12) 175.37 (0.97) 175.23 (0.83)
October 2022 175.46 (1.06) 175.27 (0.87) 175.11 (0.71)
November 2022 175.42 (1.02) 175.18 (0.78) 175.01 (0.61)

Lake Erie

Chart datum 173.50m International Great Lake Datum (1985).

Month 5% Most probable 95%
June 2022 174.72 (1.22) 174.66 (1.16) 174.62 (1.12)
July 2022 174.74 (1.24) 174.62 (1.12) 174.52 (1.02)
August 2022 174.68 (1.18) 174.54 (1.04) 174.42 (0.92)
September 2022 174.62 (1.12) 174.44 (0.94) 174.30 (0.80)
October 2022 174.54 (1.04) 174.34 (0.84) 174.16 (0.66)
November 2022 174.50 (1.00) 174.25 (0.75) 174.06 (0.56)

Lake Ontario

Chart datum 74.20m International Great Lake Datum (1985).

Month 5% Most probable 95%
June 2022 75.27 (1.07) 75.15 (0.95) 75.07 (0.87)
July 2022 75.25 (1.05) 75.04 (0.84) 74.86 (0.66)
August 2022 75.11 (0.91) 74.86 (0.66) 74.66 (0.46)
September 2022 74.96 (0.76) 74.65 (0.45) 74.48 (0.28)
October 2022 74.85 (0.65) 74.51 (0.31) 74.37 (0.17)
November 2022 74.79 (0.59) 74.50 (0.30) 74.33 (0.13)

Montreal Harbour

Chart datum 5.55m International Great Lake Datum (1985).

Month 5% Most probable 95%
June 2022 7.52 (1.97) 7.36 (1.81) 6.96 (1.41)
July 2022 7.17 (1.62) 6.72 (1.17) 6.36 (0.81)
August 2022 6.91 (1.36) 6.51 (0.96) 6.06 (0.51)
September 2022 6.80 (1.25) 6.31 (0.76) 5.81 (0.26)
October 2022 6.92 (1.37) 6.20 (0.65) 5.51 (-0.04)
November 2022 7.06 (1.51) 6.29 (0.74) 5.47 (-0.08)