Up to 50 mm widespread rains may soak southern Ontario's weekend

Heavy rain and gusty east winds to bring cool, damp conditions to southern Ontario this weekend

A rain-filled system is bringing wet conditions to southern Ontario this weekend.

After a dry finish to the workweek, rainfall began to spread across the southwest and the Greater Toronto Area (GTA) on Saturday morning. Heavy rain is expected to persist throughout the afternoon and evening, impacting outdoor plans across the region.

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An east wind off Lake Ontario is set to bring cooler air into the Golden Horseshoe, as well, with gusts forecast to reach 50-60+ km/h, adding to the brisk conditions.

Ontario Saturday evening forecast wind gusts - May 23, 2026

Weekend washout: 20-50 mm of rain is forecast in parts of Ontario through Sunday

The progression of the rain system will slow due to a high pressure area over the Maritimes, resulting in extended periods of rainfall and the potential for localized washouts in parts of southern Ontario.

By late Saturday afternoon, rain will extend into eastern Ontario and persist into Sunday, with off-and-on showers likely continuing across southern Ontario through the day.

Ontario weekend forecast rainfall totals - May 23, 2026

The heaviest rainfall totals are expected in southwestern Ontario, where atmospheric moisture could boost accumulations to 30-50 mm, particularly from Windsor to the Lake Erie shoreline and possibly Niagara.

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Lighter totals of 10-20 mm are forecast for Toronto, Ottawa, and Barrie. There is a low risk of isolated thunderstorms, and a slight chance across the southwest.

Ontario Saturday afternoon forecast conditions - May 23, 2026

Cooler daytime highs are also anticipated under dense cloud cover and rainfall: 10-12°C for Toronto, mid-to-high teens in Ottawa, and up to 20°C in Windsor.

Showers on Saturday may also impact preparations for Montreal’s Formula 1 Grand Prix on Sunday, although lower rainfall totals are expected in the city, with clearing likely later in the day.

A quick-moving system could bring additional showers and a risk of isolated thunderstorms to parts of southern Ontario late Sunday evening into Monday morning, though forecast confidence remains low for this event.

Southern Ontario Sunday thunderstorm risk - May 23, 2026

Looking ahead to the end of May, drier conditions and temperatures near 20°C are anticipated, offering a more comfortable stretch of weather.

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This weather pattern is likely to persist into the early days of June.

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