Last Frost Date Oakville — April 22 (Zone 6b/7a)

Oakville's last spring frost date is April 22 for the central core — Zone 6b. This is the historical 50th-percentile average from Environment and Climate Change Canada climate normals (1991–2020). Lakeshore neighbourhoods (Bronte, Old Oakville, Coronation Park, Lakeshore Woods) run 3–5 days earlier (April 17–20) thanks to Lake Ontario moderation, approaching Zone 7a. North Oakville (Glen Abbey north, River Oaks, Iroquois Ridge) runs 3–5 days later (April 25–30) because they sit further from Lake Ontario. The full historical range spans April 8 (earliest) to May 7 (latest).

Wait until May 1–10 to transplant tomatoes, peppers, basil, beans, and squash in Oakville's central and lakeshore neighbourhoods. North Oakville (Glen Abbey, River Oaks, Iroquois Ridge) should wait until May 5–15. Cool-season crops can be direct sown from mid-to-late March. Oakville's growing season is approximately 195 days — among the longest in Canada outside coastal BC, supporting reliable cultivation of heat-loving crops including indeterminate heirloom tomatoes, peppers, eggplant, and winter squash.

Oakville neighbourhoods vary by distance from Lake Ontario. Bronte (lakeshore west): April 17–20 (Zone 7a). Old Oakville (lakeshore central): April 17–20. Coronation Park, Lakeshore Woods: April 18–21. Eastlake, Joshua Creek: April 19–22. Glen Abbey (central): April 22–25. Iroquois Ridge (north-central): April 22–26. River Oaks (north): April 25–28. North Oakville rural / Burlington border: April 25–30. The lake-effect creates a 5–8 day spread between Oakville's lakeshore and inland neighbourhoods.

Oakville is officially Zone 6b for the central core under the Canadian Plant Hardiness Zone system. The lakeshore neighbourhoods (Bronte, Old Oakville, Coronation Park) create pockets of Zone 7a thanks to direct Lake Ontario moderation. North Oakville drops to the cooler end of Zone 6b approaching Zone 6a. A Zone 6 plant will reliably overwinter anywhere in Oakville; Zone 7 plants survive most years in lakeshore pockets but die in severe polar-vortex winters. Oakville's combination of Lake Ontario moderation and southern Ontario latitude makes it one of the friendlier climates for tender perennials in mainland Canada.

Late frost in Oakville is rare and rarely intense thanks to lake moderation — temperatures rarely drop below -2°C even in late spring cold snaps. Floating row cover (Reemay, Agribon) over transplants protects to about -3°C and is the GTA standard. Cloches or inverted pots over individual seedlings. Heavy mulch around transplants. Plant tender crops in the warmest spot — south-facing fence, lakeshore-side garden, against a heat-radiating brick wall. Available at Sheridan Nurseries Oakville (one of the largest garden centres in Canada), Plant World, Home Depot, Canadian Tire.

Oakville's April 22 last frost is among the earliest of any GTA city thanks to Lake Ontario position. Compared to other GTA cities: same as Burlington (April 22), 2 days later than Toronto and Mississauga (April 20), 1 day earlier than Hamilton (April 23), 4 days earlier than Vaughan (April 26), 6 days earlier than Brampton and Markham (April 28), 17 days earlier than Guelph (May 7). Oakville's 195-day growing season is among the longest in Canada and supports reliable harvests of every common vegetable plus tender perennials (hardy figs, certain hydrangeas) that struggle elsewhere in Ontario.