Lake Ontario water temperature
Lake Ontario, Wolfe Island (ECCC) · Lake
The current water temperature at Lake Ontario is 20.6 °C (as of September 18, 2026, source: GLOS).
Lakes stratify in summer: bathing-warm on top, markedly colder a few metres down. Measurements are taken at the surface — right where you swim.
Measurement series & statistics
This measurement series includes 165 data points since August 24, 2026.
Lowest recorded value: 20.6 °C on September 18, 2026 · highest value: 23.2 °C on September 3, 2026.
In September, temperatures have ranged between 20.6 °C and 23.2 °C.
The current value is 0.9 °C below the September average of this series.
Nearby waters
More measuring points: Lake Ontario
Frequently asked questions
Can you swim at Lake Ontario right now?
The current water temperature is 20.6 °C. See live swimming conditions, weather and quality in the BrrChecker app.
How warm is the water at Lake Ontario?
Currently 20.6 °C (updated continuously).
How warm is at Lake Ontario in September?
In September, the water temperature recently averaged 21.5 °C.
