Lake Ontario Water Temperature

(Today) Sep 2025

19.2°C / 66.6°F

The water will feel tepid. Swimming will be tolerable without a wetsuit, although it will take a little getting used to. If you intend to stay in the water for a while a 3/2mm wetsuit will be ideal.

Current weather

15°C / 59°F
(clear sky)
Partly cloudy
Wind
8 mph
Humidity
81%

Water temps is based on average surface temperatures measured throughout Lake Ontario.

Map showing Lake Ontario locations. Click on pins to view water temperature.

16 locations listed in Lake Ontario.