Lake Ontario water temperature
Lake Ontario, Niagara-on-the-Lake (ECCC) · Lake
The current water temperature at Lake Ontario is 17.3 °C (as of October 8, 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 802 data points since August 27, 2026.
Lowest recorded value: 15.0 °C on September 29, 2026 · highest value: 22.7 °C on September 4, 2026.
In October, temperatures have ranged between 17.0 °C and 18.1 °C.
The current value is 0.4 °C below the October 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 17.3 °C. See live swimming conditions, weather and quality in the BrrChecker app.
How warm is the water at Lake Ontario?
Currently 17.3 °C (updated continuously).
How warm is at Lake Ontario in October?
In October, the water temperature recently averaged 17.7 °C.
When is the water warmest at Lake Ontario?
Across the measurement record, August is on average the warmest month (22.3 °C).
