Great Lakes & Ontario Climate Zone
Ontario
Humid continental climate moderated by the Great Lakes. Four distinct seasons with hot humid summers and cold snowy winters. Toronto, Ottawa, Hamilton, London, and Kitchener. Growing season of 5–6 months. Most populous Canadian lawn market.
Seasonal Highlights
Spring
April green-up. Snow mould treatment first. Fertilise in late April–May. Overseed thin areas in May. Crabgrass pre-emergent when forsythia blooms.
Summer
Hot humid July–August. Brown patch risk in Kentucky Bluegrass. Water 25mm per week. Allow dormancy rather than stressing lawn in heat.
Fall
Prime renovation season August–September. Overseed, aerate, fertilise. Winteriser fertiliser in October.
Winter
-15°C to -25°C common. Full dormancy. Ice damage from freeze-thaw cycles in Ontario springs.
Great Lakes & Ontario Zone Monthly Calendar
Dominant Grasses
Cities in the Great Lakes & Ontario Zone
Frequently Asked Questions
Which cities are in the Great Lakes & Ontario climate zone?
The Great Lakes & Ontario climate zone includes cities such as Toronto, Ottawa, Hamilton, London, Kitchener. These cities share similar temperature ranges, growing seasons, and seasonal conditions that influence lawn care timing. Browse individual city guides for location-specific advice within the Great Lakes & Ontario zone.
What grasses grow best in the Great Lakes & Ontario climate zone?
The Great Lakes & Ontario zone is well-suited to Kentucky Bluegrass, Perennial Ryegrass, Tall Fescue, Fine Fescue. These grasses are chosen for their ability to handle the zone's key challenge: hot humid summers promoting brown patch and dollar spot. heavy clay soils in many ontario cities causing compaction and drainage issues. winter kill in exposed areas.. Select a variety that matches your lawn's sun exposure, soil type, and maintenance preferences for the best results.
When should I fertilise my lawn in the Great Lakes & Ontario zone?
In the Great Lakes & Ontario zone, fertilise in late spring once soil reaches 10°C, and most importantly in fall — a September feed for root development and an October winteriser with high potassium. The fall winteriser is the most critical fertiliser application of the year for lawns in the Great Lakes & Ontario zone.
What is the biggest lawn care challenge in the Great Lakes & Ontario zone?
The biggest challenge in the Great Lakes & Ontario zone is hot humid summers promoting brown patch and dollar spot. heavy clay soils in many ontario cities causing compaction and drainage issues. winter kill in exposed areas.. Adapting your mowing height, watering schedule, and fertiliser timing to suit this climate will keep your lawn healthy year-round. Choosing a grass variety specifically bred for great lakes & ontario conditions is the most effective first step.
How long is the growing season in the Great Lakes & Ontario zone?
The growing season in the Great Lakes & Ontario zone is approximately 6 months (hardiness zones 5a–7a). This affects when you can overseed, fertilise, and perform major lawn work. Timing all tasks within this window is critical for success — especially in zones with shorter growing seasons.