FLOOD WATCH: St. Lawrence River (Update #5)

29-May-2020 29-May-2020

This is an update to the Flood Watch statement issued by South Nation Conservation (SNC) for the St. Lawrence River on May 15, 2020.

Weather Forecast:
General rainfall up to 5 to 10 mm with a chance of moderate thunderstorms are in the forecast for Eastern Ontario starting Friday, May 29th into Saturday, May 30th. More rainfall is expected later next week.

Environmental Conditions:
According to the International Lake Ontario – St. Lawrence River Board, Lake Ontario’s water levels remain above average for this time of year but have peaked and started slowly declining. Levels are expected to continue declining in the coming weeks depending on weather conditions.

High inflows from Lake Erie continue into Lake Ontario, which will prevent any rapid lowering of Lake Ontario’s levels.

Lake Ontario’s water levels dropped to 75.34 m this week; 28 cm above average; but 52 cm below those observed at this time in 2017 and in 2019.

Levels in Lake Ontario influence levels in the upper St. Lawrence River, particularly from Kingston to Iroquois, including Maitland, Johnstown and Cardinal.

As Lake Ontario levels remain above 75.30 m, there is increased potential for shoreline flooding, flooding in low-lying areas, basement and septic system inundation,
and wave-driven erosion.

Residents are advised that strong winds may cause large waves, further aggravating water levels which may affect structures close to shore.

Residents are advised to stay away from rivers as forecasted weather may rapidly increase river flows, and banks might be unstable and slippery. Parents are encouraged to explain these dangers to their children.

Residents in flood prone or low-lying areas, historically susceptible to flooding, should take the necessary precautions to protect their property, such as:

  • Ensuring sump pump is clear, in good working condition and has a backwater valve on it.
  • Portable backup generator and pump.
  • Ensuring downspouts are clear and the outlet is at least 3 m from
    the dwelling.
  • Removing or securing items that might float away as flows increase.
  • Removing valuable items from basements or lower floors that could be subject to flooding.
  • Keep emergency phone numbers handy.
  • Familiarize yourself with your municipality’s emergency preparedness plan.

This Flood Watch statement is in effect until Friday, June 12, 2020.

SNC monitors the water levels and weather forecasts as part of the Flood Forecasting and Warning Program. Updates are provided as conditions change.

The International Lake Ontario – St. Lawrence River Board continues to monitor conditions on an ongoing basis. Information on hydrologic conditions, water levels and outflows, including graphics and photos, are available on the Board’s website at

Please visit for more information. To provide feedback with respect to changes in water related conditions please email, posted on our Facebook (/SouthNationConservation) or Twitter (@SouthNationCA).

FOR MORE INFORMATION: Geoff Owens, SNC Regulations Officer,

Taylor Campbell, SNC Communications Specialist,

Forwarded to: 
All Flood Forecasting and Warning Directory