Lake Ontario at its highest record level; Flood Watch issued.

News 100 redBy Staff

June 5th, 2019



Flood watchThe latest information provided by the International Lake Ontario – St. Lawrence River Board (ILOSLRB) indicates that Lake Ontario has remained at its record daily lake level that it first reached on June 2nd. The latest daily mean water level of 75.90 m (IGLD 1985 Datum) is the highest on record for Lake Ontario (greater than the highest daily level observed in 2017) and is approximately 84 cm above the historical average for this time of year.

While inflows from Lake Erie are at record levels, Ottawa River flows have dropped in recent days allowing outflows from Lake Ontario to increase concurrently. Further increases in Lake Ontario outflows are expected as conditions downstream permit. Lake Ontario levels may continue to rise gradually over the next several days, but that the rise is likely to be small and highly dependent on precipitation inputs.

Most scenarios are forecasting a rise of no more than 5cm above the current record levels, with the potential for a larger rise in level under the wettest scenarios.

Lake Ontario is expected to reach its seasonal peak within the next one to three weeks before it begins to slowly decline and will remain very high for the next several weeks and into the summer months.

All shoreline areas should be considered dangerous during this time. Localized flooding combined with the potential for waves to overtop breakwalls and other shoreline structures continue to make these locations extremely dangerous. Conservation Halton is asking all residents to exercise caution around Lake Ontario shoreline areas and to alert children in your care of these imminent dangers.

This Flood Watch – Lake Ontario Shoreline message will remain in effect until June 19th. Conservation Halton will continue to monitor Lake Ontario wind conditions and lake levels closely and will either terminate this message or issue further updates as necessary.

Additional information is available online through the ILOSLRB website and on Facebook:

Current Conditions:


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1 comment to Lake Ontario at its highest record level; Flood Watch issued.

  • Joe Gaetan

    Since the 1800’s the seasonal water level variability of the Great lakes has made people shudder. Starting around 1860 we have experienced both highs and lows on all of the great lakes. The Lake Ontario highs occurred around 1872, around 1952 then again around 1975. The lows on the other hand took place around 1895, 1934 and 1965. The difference between the wet and dry extremes since the 1800’s regulated and unregulated has been about 6.6 feet. Regulation has a lot to do with our current water levels. Over the past three decades, that range has been reduced to 4.3 ft. Prior to regulation, Lake Ontario levels ranged from a maximum of 248.6 ft in June 1952 to a minimum of 242.0 ft in November 1934, a total of 6.6 ft. So now that we have experienced yet another high, the question is when we will see the next low?