Lake Ontario at a Glance
| Stat | Value | |---|---| | Surface Area | 19,009 km² (7,340 sq mi) | | Maximum Depth | 244 m (802 ft) | | Average Depth | 86 m (282 ft) | | Shoreline Length | 1,146 km (712 mi) — Ontario side | | Major Ports | Toronto, Hamilton, Kingston, Cobourg, Whitby, Rochester (US) | | Primary Inflow | Niagara River (from Lake Erie) | | Outflow | St. Lawrence River |
Weather Patterns
Lake Ontario is the most unpredictable of the Great Lakes for recreational boaters. Its east-west orientation funnels prevailing westerlies into massive swells with minimal fetch protection.
Key Weather Hazards
- Sudden Squalls: Afternoon thunderstorms in July and August can materialize within 15 minutes. Monitor Environment Canada marine forecast continuously.
- Lake Effect Convergence: When cold arctic air moves over the relatively warm lake surface, violent wind shear develops, particularly near the eastern basin (Kingston to Prince Edward County).
- Fog: Spring fog is persistent, especially where warm air meets cold lake water (April-June). Carries visibility below 100 meters. Navigation lights, radar reflectors, and sound signals become mandatory.
- Wave Heights: 2-4 metre waves are common in sustained westerlies. The western basin between Hamilton and Toronto is particularly exposed.
Shipping Lanes and Commercial Traffic
Lake Ontario is a major commercial waterway connecting the St. Lawrence Seaway to the upper Great Lakes via the Welland Canal. Recreational boaters MUST be aware of:
- Designated shipping channels entering Hamilton Harbour, Toronto Harbour, and the approaches to the Welland Canal at Port Weller.
- Laker vessels (up to 225m long) have extremely limited maneuverability and cannot alter course quickly. You are ALWAYS the give-way vessel near commercial ships.
- Security zones around the Pickering and Darlington nuclear generating stations — enforced exclusion zones exist within 250m of the intake structures.
Best Recreational Zones
Western Basin (Hamilton to Toronto)
- Protected by the Toronto Islands. Toronto Harbour offers sheltered cruising, marinas, and island beaches.
- Hamilton Harbour connects to the Royal Botanical Gardens and Cootes Paradise.
- Heavy traffic on summer weekends.
Central Basin (Cobourg to Prince Edward County)
- Excellent salmon trolling grounds. Deep water close to shore.
- Presqu'ile Provincial Park offers protected anchorage.
- The Sandbanks region is Ontario's premier beach destination.
Eastern Basin (Kingston to Cornwall)
- The Thousand Islands archipelago is world-class cruising territory.
- Kingston is the freshwater sailing capital of Canada.
- Historic Rideau Canal entrance at Kingston Mills.
Fishing on Lake Ontario
Lake Ontario supports one of the most productive sport fisheries in North America:
- Chinook Salmon (King): April-September, trolling at 50-100 foot depths
- Coho Salmon: Best in September-October near tributaries
- Lake Trout: Year-round, deep structure trolling
- Steelhead (Rainbow Trout): Spring and fall tributary runs
- Walleye: Bay of Quinte is the premier destination
- Smallmouth Bass: Thousand Islands is legendary
See our full Ontario Fishing Zones guide for specific FMZ regulations.
Essential Contacts
- Canadian Coast Guard (Marine Emergency): VHF Channel 16 or call *16 on cell phone
- Environment Canada Marine Forecast: weather.gc.ca/marine
- OPP Marine Unit: Report impaired boaters: 1-888-310-1122
Vessel Compliance: Before entering any Ontario port, ensure your PCL numbers meet Transport Canada's 3-inch block letter requirement. OPP Marine patrols are active in all major harbours. Order marine-grade lettering.