Southern Ontario will face a significant weather shift this week as a powerful Colorado low pushes into the region. Forecasters are warning that the approaching system will bring unseasonable heat along with a heightened risk of severe thunderstorms, large hail, strong winds, and heavy rain. After a calm and pleasant Monday, conditions will change dramatically on Tuesday. Much of Southern Ontario will see temperatures climb into the mid- to high-20s, with parts of Southwestern Ontario possibly hitting 30°C. If so, it would mark the first 30-degree day in Canada this year.
This early-season heat is being driven by a low-pressure system moving into northeastern Ontario. As it advances, it pulls in a warm and moisture-laden air mass from the south. As a result, temperatures could rise 8°C to 10°C above the seasonal average. Dew point levels may also approach 20°C, making the air feel uncomfortably humid.
Heightened Risk of Severe Thunderstorms
However, the heat will come with risks. Forecasters warn that the combination of warmth and moisture could trigger severe thunderstorms across the region. According to The Weather Network’s Forecast Centre, “the main hazards with any severe storm that forms will be large hail, strong winds and heavy downpours.”
The storm threat could also include isolated tornadoes. “There is a low, but non-zero risk of an isolated tornado or two with favourable, low-level shear and low cloud bases present,” the Forecast Centre explained. These conditions may lead to rotating thunderstorms if individual storm cells remain isolated.
Storm Timing and Impact Zones
Meteorologists expect showers and storms to develop throughout the day, with the most severe activity likely to occur between 3 p.m. and 8 p.m. Central Ontario, Georgian Bay, and northeastern regions of the province are most at risk, though other parts of Southern Ontario may also experience strong storms.
Wind gusts in the strongest cells could exceed 100 km/h. Although the storms are expected to move quickly—typically under 60 km/h—there remains a risk of localized flooding due to heavy downpours. Hailstones measuring 2 to 4 cm in diameter, roughly the size of ping pong balls, could also occur due to cold air aloft and strong upward motion in the atmosphere.
A Calm Start Before the Turbulence
Before the stormy weather arrives, Ontarians will enjoy a tranquil Monday. Thanks to a ridge of high pressure, the day will bring mild temperatures near 20°C and stable conditions—ideal for those heading to the polls during the federal election.
Officials Urge Preparedness
In light of the storm threat, officials are encouraging residents to remain alert and ready. “Monitor the forecast on Tuesday and stay aware of potential watches and warnings in your community,” The Weather Network advised.
To prepare, residents should secure outdoor items, ensure emergency kits are stocked, and monitor weather alerts throughout the day.
While Tuesday offers a glimpse of summer, it also brings serious weather concerns. As the Colorado low passes through, Ontarians must remain cautious amid the risk of damaging storms and possible tornadoes.
