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%
November 2022 183.57 (0.37) 183.54 (0.34) 183.51 (0.31)
December 2022 183.53 (0.33) 183.46 (0.26) 183.41 (0.21)
January 2023 183.46 (0.26) 183.37 (0.17) 183.31 (0.11)
February 2023 183.40 (0.20) 183.30 (0.10) 183.23 (0.03)
March 2023 183.38 (0.18) 183.27 (0.07) 183.18 (-0.02)
April 2023 183.43 (0.23) 183.30 (0.10) 183.18 (-0.02)

Lake Huron

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

Month 5% Most probable 95%
November 2022 176.60 (0.60) 176.56 (0.56) 176.52 (0.52)
December 2022 176.60 (0.60) 176.50 (0.50) 176.43 (0.43)
January 2023 176.58 (0.58) 176.46 (0.46) 176.35 (0.35)
February 2023 176.57 (0.57) 176.46 (0.46) 176.31 (0.31)
March 2023 176.61 (0.61) 176.46 (0.46) 176.31 (0.31)
April 2023 176.72 (0.72) 176.54 (0.54) 176.34 (0.34)

Lake St. Clair

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

Month 5% Most probable 95%
November 2022 175.22 (0.82) 175.15 (0.75) 175.09 (0.69)
December 2022 175.28 (0.88) 175.13 (0.73) 175.00 (0.60)
January 2023 175.34 (0.94) 175.14 (0.74) 174.88 (0.48)
February 2023 175.36 (0.96) 175.12 (0.72) 174.86 (0.46)
March 2023 175.40 (1.00) 175.18 (0.78) 174.92 (0.52)
April 2023 175.50 (1.10) 175.26 (0.86) 174.95 (0.55)

Lake Erie

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

Month 5% Most probable 95%
November 2022 174.32 (0.82) 174.24 (0.74) 174.20 (0.70)
December 2022 174.40 (0.90) 174.21 (0.71) 174.08 (0.58)
January 2023 174.45 (0.95) 174.21 (0.71) 174.02 (0.52)
February 2023 174.50 (1.00) 174.22 (0.72) 173.96 (0.46)
March 2023 174.62 (1.12) 174.32 (0.82) 174.03 (0.53)
April 2023 174.73 (1.23) 174.45 (0.95) 174.16 (0.66)

Lake Ontario

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

Month 5% Most probable 95%
November 2022 74.49 (0.29) 74.40 (0.20) 74.33 (0.13)
December 2022 74.62 (0.42) 74.43 (0.23) 74.28 (0.08)
January 2023 74.71 (0.51) 74.47 (0.27) 74.25 (0.05)
February 2023 74.88 (0.68) 74.48 (0.28) 74.22 (0.02)
March 2023 74.97 (0.77) 74.61 (0.41) 74.31 (0.11)
April 2023 75.24 (1.04) 74.85 (0.65) 74.58 (0.38)

Montreal Harbour

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

Month 5% Most probable 95%
November 2022 5.66 (0.11) 5.38 (-0.17) 5.27 (-0.28)
December 2022 6.35 (0.80) 5.85 (0.30) 5.38 (-0.17)
January 2023 6.63 (1.08) 6.20 (0.65) 5.62 (0.07)
February 2023 7.00 (1.45) 6.45 (0.90) 5.73 (0.18)
March 2023 7.23 (1.68) 6.60 (1.05) 5.80 (0.25)
April 2023 7.80 (2.25) 7.21 (1.66) 6.24 (0.69)